Structure and Bonding
Structure and Bonding and States of Matter
GCSE Workbook
Mr Singh
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Structure and Bonding
4.1.3.2 Typical properties Content
Key opportunities for skills development
Many transition elements have ions with different charges, form coloured compounds and are useful as catalysts. Students should be able to exemplify these general properties by reference to compounds of Cr, Mn, Fe, Co, Ni, Cu.
4.2 Bonding, structure, and the properties of matter Chemists use theories of structure and bonding to explain the physical and chemical properties of materials. Analysis of structures shows that atoms can be arranged in a variety of ways, some of which are molecular while others are giant structures. Theories of bonding explain how atoms are held together in these structures. Scientists use this knowledge of structure and bonding to engineer new materials with desirable properties. The properties of these materials may offer new applications in a range of different technologies.
4.2.1 Chemical bonds, ionic, covalent and metallic 4.2.1.1 Chemical bonds Content
Key opportunities for skills development
There are three types of strong chemical bonds: ionic, covalent and metallic. For ionic bonding the particles are oppositely charged ions. For covalent bonding the particles are atoms which share pairs of electrons. For metallic bonding the particles are atoms which share delocalised electrons. Ionic bonding occurs in compounds formed from metals combined with non-metals. Covalent bonding occurs in most non-metallic elements and in compounds of non-metals. Metallic bonding occurs in metallic elements and alloys. Students should be able to explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons.
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016 Structure and Bonding
4.2.1.2 Ionic bonding Content
Key opportunities for skills development
When a metal atom reacts with a non-metal atom electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions. The ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0).
MS 5b Visualise and represent 2D and 3D forms including twodimensional representations of 3D objects.
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride
Students should be able to draw dot and cross diagrams for ionic compounds formed by metals in Groups 1 and 2 with non-metals in Groups 6 and 7.
WS 1.2
The charge on the ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 relates to the group number of the element in the periodic table. Students should be able to work out the charge on the ions of metals and non-metals from the group number of the element, limited to the metals in Groups 1 and 2, and non-metals in Groups 6 and 7.
4.2.1.3 Ionic compounds Content
Key opportunities for skills development
An ionic compound is a giant structure of ions. Ionic compounds are MS 5b held together by strong electrostatic forces of attraction between Visualise and represent 2D oppositely charged ions. These forces act in all directions in the and 3D forms including twolattice and this is called ionic bonding. dimensional representations The structure of sodium chloride can be represented in the following of 3D objects. forms:
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Structure and Bonding
Content
Key opportunities for skills development
Students should be able to:
WS 1.2
MS 4a • deduce that a compound is ionic from a diagram of its structure in one of the specified forms MS 1a, 1c • describe the limitations of using dot and cross, ball and stick, two and three-dimensional diagrams to represent a giant ionic structure • work out the empirical formula of an ionic compound from a given model or diagram that shows the ions in the structure. Students should be familiar with the structure of sodium chloride but do not need to know the structures of other ionic compounds.
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016 Structure and Bonding
4.2.1.4 Covalent bonding Content
Key opportunities for skills development
When atoms share pairs of electrons, they form covalent bonds. These bonds between atoms are strong.
WS 1.2
Covalently bonded substances may consist of small molecules. Students should be able to recognise common substances that consist of small molecules from their chemical formula.
Recognise substances as small molecules, polymers or giant structures from diagrams showing their bonding.
Some covalently bonded substances have very large molecules, such as polymers. Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide. The covalent bonds in molecules and giant structures can be represented in the following forms:
Polymers can be represented in the form:
where n is a large number.
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Structure and Bonding
Content
Key opportunities for skills development
Students should be able to:
MS 5b
• draw dot and cross diagrams for the molecules of hydrogen, chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane • represent the covalent bonds in small molecules, in the repeating units of polymers and in part of giant covalent structures, using a line to represent a single bond • describe the limitations of using dot and cross, ball and stick, two and three-dimensional diagrams to represent molecules or giant structures • deduce the molecular formula of a substance from a given model or diagram in these forms showing the atoms and bonds in the molecule.
4.2.1.5 Metallic bonding Content
Key opportunities for skills development
Metals consist of giant structures of atoms arranged in a regular pattern.
WS 1.2
The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds. The bonding in metals may be represented in the following form:
Recognise substances as metallic giant structures from diagrams showing their bonding. MS 5b Visualise and represent 2D and 3D forms including twodimensional representations of 3D objects.
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016 Structure and Bonding
4.2.2 How bonding and structure are related to the properties of substances 4.2.2.1 The three states of matter Content
Key opportunities for skills development
The three states of matter are solid, liquid and gas. Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point.
MS 5b
Visualise and represent 2D and 3D forms including twoThe three states of matter can be represented by a simple model. In dimensional representations this model, particles are represented by small solid spheres. of 3D objects. Particle theory can help to explain melting, boiling, freezing and condensing.
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance. (HT only) Limitations of the simple model above include that in the model there are no forces, that all particles are represented as spheres and that the spheres are solid. WS 1.2
Students should be able to: • predict the states of substances at different temperatures given appropriate data • explain the different temperatures at which changes of state occur in terms of energy transfers and types of bonding • recognise that atoms themselves do not have the bulk properties of materials • (HT only) explain the limitations of the particle theory in relation to changes of state when particles are represented by solid inelastic spheres which have no forces between them.
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Structure and Bonding
4.2.2.2 State symbols Content
Key opportunities for skills development
In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions. Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification.
4.2.2.3 Properties of ionic compounds Content
Key opportunities for skills development
Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions. These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds. When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow. Knowledge of the structures of specific ionic compounds other than sodium chloride is not required.
4.2.2.4 Properties of small molecules Content
Key opportunities for skills development
Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
WS 1.2
These substances have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils. The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points. These substances do not conduct electricity because the molecules do not have an overall electric charge. Students should be able to use the idea that intermolecular forces are weak compared with covalent bonds to explain the bulk properties of molecular substances.
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016 Structure and Bonding
4.2.2.5 Polymers Content
Key opportunities for skills development
Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature. Students should be able to recognise polymers from diagrams showing their bonding and structure.
4.2.2.6 Giant covalent structures Content
Key opportunities for skills development
Substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
MS 5b
Students should be able to recognise giant covalent structures from diagrams showing their bonding and structure.
Visualise and represent 2D and 3D forms including twodimensional representations of 3D objects. WS 1.2
4.2.2.7 Properties of metals and alloys Content
Key opportunities for skills development
Metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points. In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped. Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder. Students should be able to explain why alloys are harder than pure WS 1.2 metals in terms of distortion of the layers of atoms in the structure of a pure metal.
4.2.2.8 Metals as conductors Content
Key opportunities for skills development
Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal. Metals are good conductors of thermal energy because energy is transferred by the delocalised electrons.
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Structure and Bonding
4.2.3 Structure and bonding of carbon 4.2.3.1 Diamond Content
Key opportunities for skills development
In diamond, each carbon atom forms four covalent bonds with other MS 5b carbon atoms in a giant covalent structure, so diamond is very hard, Visualise and represent 2D has a very high melting point and does not conduct electricity. and 3D forms including twodimensional representations of 3D objects. Students should be able to explain the properties of diamond in terms of its structure and bonding.
WS 1.2
4.2.3.2 Graphite Content
Key opportunities for skills development
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers.
WS 1.2
In graphite, one electron from each carbon atom is delocalised. Students should be able to explain the properties of graphite in terms of its structure and bonding. Students should know that graphite is similar to metals in that it has delocalised electrons.
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016 Structure and Bonding
4.2.3.3 Graphene and fullerenes Content
Key opportunities for skills development
Graphene is a single layer of graphite and has properties that make WS 1.2, 1.4 it useful in electronics and composites. MS 5b Students should be able to explain the properties of graphene in Visualise and represent 2D terms of its structure and bonding. and 3D forms including twoFullerenes are molecules of carbon atoms with hollow shapes. The dimensional representations structure of fullerenes is based on hexagonal rings of carbon atoms of 3D objects. but they may also contain rings with five or seven carbon atoms. The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape. Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials. Students should be able to: • recognise graphene and fullerenes from diagrams and descriptions of their bonding and structure • give examples of the uses of fullerenes, including carbon nanotubes.
4.2.4 Bulk and surface properties of matter including nanoparticles (chemistry only) 4.2.4.1 Sizes of particles and their properties Content
Key opportunities for skills development
Nanoscience refers to structures that are 1–100 nm in size, of the order of a few hundred atoms. Nanoparticles, are smaller than fine particles (PM2.5), which have diameters between 100 and 2500 nm (1 x 10-7 m and 2.5 x 10-6 m). Coarse particles (PM10) have diameters between 1 x 10-5 m and 2.5 x 10-6 m. Coarse particles are often referred to as dust.
WS 1.2, 1.4, 4.1, 4.2, 4.3 4.4, 4.5 MS 2h Make order of magnitude calculations.
As the side of cube decreases by a factor of 10 the surface area to MS 5c volume ratio increases by a factor of 10. Calculate areas of triangles Nanoparticles may have properties different from those for the and rectangles, surface same materials in bulk because of their high surface area to areas and volumes of cubes. volume ratio. It may also mean that smaller quantities are needed to be effective than for materials with normal particle sizes.
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Structure and Bonding
Content
Key opportunities for skills development
Students should be able to compare ‘nano’ dimensions to typical dimensions of atoms and molecules.
MS 1b Recognise and use expressions in standard form. MS 1c Use ratios, fractions and percentages. MS 1d Make estimates of the results of simple calculations.
4.2.4.2 Uses of nanoparticles Content
Key opportunities for skills development
Nanoparticles have many applications in medicine, in electronics, in cosmetics and sun creams, as deodorants, and as catalysts. New applications for nanoparticulate materials are an important area of research. Students should consider advantages and disadvantages of the applications of these nanoparticulate materials, but do not need to know specific examples or properties other than those specified. Students should be able to:
WS 1.3, 1.4, 1.5
• given appropriate information, evaluate the use of nanoparticles for a specified purpose • explain that there are possible risks associated with the use of nanoparticles.
4.3 Quantitative chemistry Chemists use quantitative analysis to determine the formulae of compounds and the equations for reactions. Given this information, analysts can then use quantitative methods to determine the purity of chemical samples and to monitor the yield from chemical reactions. Chemical reactions can be classified in various ways. Identifying different types of chemical reaction allows chemists to make sense of how different chemicals react together, to establish patterns and to make predictions about the behaviour of other chemicals. Chemical equations provide a means of representing chemical reactions and are a key way for chemists to communicate chemical ideas.
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Structure and Bonding
Helping yourself
Read the section on Bonding and Structure in your textbook Read the relevant sections of these websites bbc.co.uk/schools/gcsebitesize/chemistry gcsescience.com docdrown.info revisioncentre.co.uk youtube for video tutorials other teachers!
Mr Singh
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Structure and Bonding
4th Form
Overview of Structure and Bonding Brick Arrangement (Structure) A brick wall consists of two parts: the bricks and mortar. The bricks form the substance of the wall and the mortar bonds them all together. Similarly, all chemical substances are made up of atoms and bonds. The atoms are the Bricks (atoms)
Mortar (bonding)
substance and the chemical bonds hold them all together. There are also different ways in which you can arrange the bricks in a wall and they will produce walls of different strengths. So also in compounds, atoms can be arranged in different fashions and will produce different melting and boiling points. The arrangement of atoms is what we call ...................... structure. There are 118 different types of atoms (the bricks) known which we call ‘The .............................’ There are 4 different types of chemical ............... (mortar) we will learn about: Ionic bonding, Covalent Bonding, Metallic Bonding and Simple Molecular Forces. There are 4 main chemical structures (brick arrangements) we will learn about: Giant Ionic structures , Giant Covalent structures, Simple Molecular Structures and Metallic Structures.
Mr Singh
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Structure and Bonding
Ionic Bonding - electron transfer Ionic bonds are formed by one atom ........................ electrons to another atom to form .................... . Ions are atoms, or groups of atoms, which have lost or gained ............................. The atom losing electrons forms a ....................... ion (a cation) and is usually a metal. The overall charge on the ion is positive due to excess positive nuclear charge (protons do NOT change in chemical reactions). The atom gaining electrons forms a ................... ion (an anion) and is usually a non-metallic element. The overall charge on the ion is negative because of the gain, and therefore excess, of negative electrons. Example 1: A Group 1 metal + a Group 7 non-metal e.g. sodium + chlorine ==> sodium chloride NaCl or ionic formula Na+ClIn terms of electron arrangement, the sodium donates its outer electron to a chlorine atom forming a single positive sodium ion and a single negative chloride ion. The atoms have become stable ions, because electronically, sodium becomes like neon and chlorine like argon. Na (2.8.1) + Cl (2.8.7) ==> Na+ (2.8) Cl- (2.8.8)
ONE
combines with ONE
to form
Example 2: A Group 2 metal + a Group 7 non-metal e.g. magnesium + chlorine ==> magnesium chloride MgCl2 or ionic formula Mg2+(Cl-)2 In terms of electron arrangement, the magnesium donates its two outer electrons to two chlorine atoms forming a double positive magnesium ion and two single negative chloride ions. The atoms have become stable ions, because electronically, magnesium becomes like neon and chlorine like argon. Mg (2.8.2) + 2Cl (2.8.7) ==> Mg2+ (2.8) 2Cl- (2.8.8)
ONE
combines with TWO
to form
Example 3: A Group 3 metal + a Group 7 non-metal e.g. aluminium + fluorine ==> aluminium fluoride AlF3 or ionic formula Al3+(F-)3 In terms of electron arrangement, the aluminium donates its three outer electrons to three fluorine atoms forming a triple positive aluminium ion and three single
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Structure and Bonding
negative fluoride ions. The atoms have become stable ions, because electronically, aluminium and fluorine becomes electronically like neon. Al (2.8.3) + 3F (2.7) ==> Al3+ (2.8) 3F- (2.8)
ONE
combines with THREE
to form
Example 4: A Group 1 metal + a Group 6 non-metal e.g. potassium + oxygen ==> potassium oxide K2O or ionic formula (K+)2O2In terms of electron arrangement, the two potassium atoms donates their outer electrons to one oxygen atom. This results in two single positive potassium ions to one double negative oxide ion. All the ions have the stable electronic structures 2.8.8 (argon like) or 2.8 (neon like). 2K (2.8.8.1) + O (2.6) ==> 2K+ (2.8.8) O2- (2.8)
TWO
combine with ONE
to form
Example 5: A Group 2 metal + a Group 6 non-metal e.g. calcium + oxygen ==> calcium oxide CaO or ionic formula Ca2+O2In terms of electron arrangement, one calcium atom donates its two outer electrons to one oxygen atom. This results in a double positive calcium ion to one double negative oxide ion. All the ions have the stable electronic structures 2.8.8 (argon like) or 2.8 (neon like). Ca (2.8.8.2) + O (2.6) ==> Ca2+ (2.8.8) O2- (2.8)
ONE
combines with ONE
to form
Example 6: A Group 3 metal + a Group 6 non-metal e.g. aluminium + oxygen ==> aluminium oxide Al2O3 or ionic formula (Al3+)2(O2-)3 In terms of electron arrangement, two aluminium atoms donate their three outer
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Structure and Bonding
electrons to three oxygen atoms. This results in two triple positive aluminium ions to three double negative oxide ions. All the ions have the stable electronic structure of neon 2.8. 2Al (2.8.3) + 3O (2.6) ==> 2Al3+ (2.8) 3O2- (2.8)
TWO
Mr Singh
combine with THREE
to form
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Structure and Bonding
Covalent Bonding Covalent Bonding Elements bond to gain a full outer shell of electrons. They try to imitate the electronic arrangement of ……………………. GASES. Covalent bonding involves the sharing of valence (‘outer shell’) electrons to form covalent bonds. These bonds are strong and are difficult to break. They are comprised of NON-METAL elements. A pair of electrons signifies a single covalent bond. Atoms are held together by the attraction between the shared electrons and the nuclei of the bonding atoms.
Hydrogen (H2)
2 x
Water (H2O)
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Structure and Bonding
Methane (CH4)
Hydrogen Chloride (HCl)
Chlorine
Double and triple covalent bonding A double bond has four shared electrons. An example of this is the oxygen molecule.
Oxygen (O2)
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Structure and Bonding
Nitrogen (N2) – A nitrogen molecule has a triple bond.
Carbon dioxide – contains two double bonds.
Other examples:
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Structure and Bonding
Ammonia (NH3)
Ethane (C2H6)
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Structure and Bonding
Representing Molecules Empirical formula
Molecular formula
A molecular formula simply counts the number of each sort of atom present in the molecule. It tells us nothing about how they are all put together. These are usually only used in equations when the structure of a molecule doesn’t matter. e.g.
propane is !! !! butane is !! !!" !! !! ! + 5!! ! → 3!!! ! + 4!! !(!)
Structural formula
A structural formula shows how atoms are joined together. e.g. propane !!! !!! !!! 4 carbon alkane: !!! !!! !!! !!! or !!! !" !!! !!!
Display formula
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Structure and Bonding
A display formula shows all the bonds in the molecule as individual lines. Each line represents a ……………………………. electrons.
ethanol Display
Ball and Stick
Wedge and Dash Space filled
butane Notice that the display formula of butane doesn’t show the shape of the molecule. Display formulae always show the bonds flattened out. What this means is that the display formula will often be twisted at angles but still be the same molecule. Be careful. Display formulae are only used for small molecules because it is very time consuming.
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Structure and Bonding
Addition Polymerisation Plastics are materials which soften on …………………….. and harden on ………………………….. They are therefore very useful for moulding. There are two kinds: thermo…………………….. plastics and therm………………….. plastics. The later can only be heated and cooled once.
Plastics are strong relative to their mass. They are usually soft and flexible. They are very good insulators. They have a huge number of uses.
Under the right conditions molecules containing carbon-carbon double bonds can join to produce very long chains. Part of the double bond is broken, and the electrons in it are used to join to neighbouring molecules. This is called ………………….. …………………….
Polymerisation is the joining up of little molecules (MONOMERS) to make one big molecule (the POLYMER). Many Monomer ss
Single Polymer
Ethene
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Structure and Bonding
In the case of ethene, lots of ethene molecules join together to make ………………………
Chains can vary from about 4000 to 40,000 carbon atoms
Polyethene comes in two types. High Density Polyethene (HDPE) which is used in plastic milk bottles and the like and Low Density Polyethene (LDPE) which is used to make clingfilm.
It’s much easier to work out what polymer is produced if we tuck everything either above or below the carbon-carbon double bond.
Propene
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Structure and Bonding
This is known as Polypropene (PP) and is used for making ropes and crates. They have the recycling mark PP
Chloroethene
This is known as Polychloroethene (PVC) and has lots of uses. It is quite strong and rigid and so can be used for drainpipes or replacement windows. By the addition of a ………………………….. it can be made flexible and so is used in sheet flooring and even cloths. PVC is a very good insulator so is used to coat wiring.
These plastics are known as Thermosoftening plastics because when you heat them, they melt but then re-solidify. Even though there are very strong covalent bonds in the molecule, the bond between the molecules are quite weak.
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Structure and Bonding
Giant Metallic Structure In metals the atoms are packed tightly together in a ……………………… pattern. The outer electrons get separated from the atom. The result is a …………………….. of positive ions in a sea of ……………………………………. electrons. Copper is an example of a metal.
The copper ions are held together by their ……………………………………. to the electrons shared between them. The strong electrostatic forces of attraction are called …………………………. bonds. The regular arrangement of atoms in a lattice results in a …………………………… of copper. A piece of copper wire will contain millions of tiny grains of copper which can be seen under a microscope. The way atoms are packed together depends on the metal. There are several possible arrangements but they are always regular. Properties All metals are different but they all share these general properties to some extent:
Mr Singh
1.
They are usually ………………………., they won’t bend or dent easily.
2.
They are usually ………………….. When you hammer them, they won’t break up easily.
3.
They usually have high compressive …………………………... You have to compress them very hard before they deform.
4.
They usually have very high tensile ………………………….. You have to put them under a lot of tension before they stretch and break.
5.
Most metals can be bent or shaped with
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Structure and Bonding
sufficient force. They are …………………………… and ductile. This is because the layers of atoms can slide over each other without the metallic bonds breaking. The bond just rearrange. 6.
The are good conductors of ………………………………., because the electrons can move through the lattice carrying charge.
7.
The are good conductors of ……………………………. The free electrons take in heat energy which makes them move faster. They spread through the lattice.
8.
They usually have …………………………….. melting points because it takes a lot of heat energy to break the strong metallic bonds.
9.
They are usually ……………………………. because the atoms are packed together tightly.
The grains in metals are not perfect. The grains or crystals contain vacant sites where missing are missing and dislocations where a whole row of atoms are missing. The edge of the grain is known as the grain boundary.
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Structure and Bonding
102 WS
States of Matter Matter is what everything is made up of. There are 3 types of matter. These are known as the States of Matter. They are: _______________ _______________ _______________ It is possible to change a substance’s state of matter. Fill in the spaces in the triangle below:
GAS
Sublimation
Condensing
SOLID
Each change of state is because of heat energy. If heat is taken in then the change is endothermic. If heat is given out then it is exothermic. Questions Identify the six changes of state shown above as either endothermic or exothermic. For melting, explain the answer you have given.
When you have taken a dog for a walk on a cold day the windows in the car ‘fog up’. Explain why this is.
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Structure and Bonding
102 WS
The arrangement of particles All matter is made up of particles. The properties of any matter can be explained by the way in which the particles are arranged. SOLID LIQUID GAS solid Liquid gas Particles close together Particles close together Particles spread out Regular arrangement - Irregular arrangement Random arrangement lattice No gaps between Gaps between particles Particles spread out particles Particles can not move Particles can move about Particles can move about about – only vibrate! With a tick, show which states of matter exhibit which of the following properties: SOLID LIQUID GAS Property Fixed volume Fixed shape Dense Hard Can flow Liquids and gases can diffuse. What does this mean? Explain in terms of particle arrangement.
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Structure and Bonding
Giant Ionic Structure One of the most common ionic solids is sodium chloride (ordinary table salt).
In sodium chloride, the sodium and chloride ions are packed in a ………………….. and are held together with strong ……………………….. bonds. Ionic bonds are strong ………………………………. attractions between ions of opposite charge. The result is that ionic substances are …………………………. and result in crystals. A crystal of salt is very small and a pinch of salt contains many millions.
All ionic compounds form regular ………………………….. structures. They are giant structures because the lattice carries on infinitely. Their properties 1. They have high melting and boiling points. 2. Substance Melting point/° C Sodium chloride 801 Magnesium oxide 2852 Aluminium oxide 2072
Boiling point/° C 1413 3600 2980
This is because ionic bonds are very ……………………… so it takes a lot of heat energy to breakup the lattice and from a liquid. All ionic substances are solid at room temperature.
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Structure and Bonding
3.
They shatter when hit with a hammer: they are ……………………………
4.
They are usually …………………………. in water, but insoluble in other nonpolar solvents such as hexane.
5.
They ……………………….. conduct electricity when solid. Electricity is the movement of charged particles and although the ions are charged, they cannot move because they are firmly held in position.
6.
They…………………..conduct electricity when molten or dissolved. This is because the ions are now free to move.
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Structure and Bonding
Simple Molecular Structures Iodine is a good example of a ……………………….. solid. Each iodine molecule consists of two atoms held together by strong ………………….. bonds.
The molecules are packed in a ……………… and held together by …………… intermolecular forces. This pattern is repeated millions of times and the result is a crystal. Iodine crystals are grey-black, shiney and brittle. A jar would contain hundreds of thousands of them. Iodine is like all simple molecular solids. All the molecules are held together in a lattice. So the are …………………... The forces that hold the molecules together are weak – much weaker than within the molecules Properties 1. They have ……………….. melting and boiling points. This is because it doesn’t take much heat energy to overcome the weak forces between molecules. Infact, the majority of simple molecular componds boil below room temperature so are gases or liquids. Substance Oxygen Chlorine Water Napthalene 2. 3. 4.
Mr Singh
Melting Point/° C -219 -101 0 80
Boiling Point/° C -183 -35 100 218
They shatter when hit with a hammer: they are ………………………. Simple molecular solids are usually ……………………. in water but soluble in non-polar solvents such as ………………………... They do not conduct ………………………. Molecules are not charged so cannot conduct, even when molten. Solids Iodine Sulfur Napthalene Liquids Bromine Water Ethanol Gases Oxygen Nitrogen Carbon dioxide
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Structure and Bonding
Molecular Compounds All Molecules have very strong covalent bonds between their atoms. But molecules are small and discrete and the forces between molecules are very weak. The forces between molecules are called Intermolecular Forces (IMF) or Van der Waal forces.
The Strength of the Inter Molecular Forces determines a number of physical properties of chemical compounds. a) Melting Point b) Boiling point c) Viscosity d) Surface Tension The strength of the intermolecular forces depends chiefly on the size and shape of the molecule. The greater the area for molecules to overlap, the stronger the intermolecular forces.
All Molecules have a low melting and boiling point compared to compounds with ionic bonds. This explains why most molecules are gases at room temperature.
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3rd form notes
Structure and Bonding
Giant Covalent Structures Both Graphite and Diamond are ………………………………. of carbon. Allotropes are two or more forms of the same element in the same state. Diamond In diamond, the carbon atoms form a ………………………….
A carbon atom forms covalent bonds with ……………………. others. Each other atom then bonds to three more and so on. Eventually millions of carbon atoms are bonded together in a ………………………….. covalent structure. It is a giant structure because the pattern goes on forever. This results in a single crystal of diamond. It is extrememly hard and has one of the highest melting points known of any chemical substance. There are no free electrons so it doesn’t conduct electricity. Graphite In graphite, the carbon atoms from flat sheets of graphene.
Each carbon atom forms covalent bonds to ………………………. others. This gives rings of six atoms. These join to make flat sheets that lie on top of each other. These are held together by weak …………………………………………. forces. A look at a lump of graphite shows up its layered structure. Of the four outer electrons that carbon has only three are involved in bonding. There forth is ……………………………….. and free to move through the graphite structure. Graphite is therefore a
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3rd form notes
Structure and Bonding
conductor of ………………………………………. This also makes it shiny in appearance. Graphite is slippery because the …………………………. bonding between the layers mean that they are able to slide over each other easily. This is why graphite leaves a mark when rubbed against paper. Both these allotropes of carbon have giant covalent structures. Allotrope Diamond
Graphite
Property The hardest substance known Very high melting and boiling point (3550 ° C) Does not conduct electricity Sparkles when cut Soft and slippery
Reason Very strong covalent bonds in three-dimensions Very strong covalent bonds in three-dimensions
Use Drilling and cutting tools Drilling and cutting tools
There are no ion for free electrons It has a regular structure The layers of grapheme can slide over each other
Conducts electricity
Each atom has four other electrons but only three are involved in bonding. The fourth can therefore move through the graphite carrying charge
Drilling and cutting tools Jewellery As a lubricant for locks and lead in pencils For electrodes and as connecting brushes in dynamos and motors
There are also other allotropes of carbon. The carbon nanotube is the basis of all the nano-technology industry.
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Structure and Bonding
Buckminster Fullerene A 3rd form of carbon are fullerenes or 'bucky balls'! It consists of hexagonal rings like graphite and alternating pentagonal rings to allow curvature of the surface. Buckminster Fullerene C60 is shown and the bonds form a pattern like a soccer ball. Others are oval shaped like a rugby ball. They are NOT considered giant covalent structures and are classed as simple! molecules. They do dissolve in solvents, and although solid, their melting points are not that high. They are mentioned here to illustrate the different forms of carbon AND they are trying to make them as continuous tubes to form very strong fibres of 'pipe like' molecules called 'nanotubes'.
TYPICAL PROPERTIES of GIANT COVALENT STRUCTURES This type of giant covalent structure is thermally very stable and has a very high melting and boiling points because of the strong covalent bond network They are usually poor conductors of electricity because the electrons are not usually free to move as they can in metallic structures. Also because of the strength of the bonding in all directions in the structure, they are often very hard, strong and will not dissolve in solvents like water. The hardness of diamond enables it to be used as the 'leading edge' on cutting tools.
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Structure and Bonding
Silicon dioxide (silica, SiO2) has a similar 3D structure and properties, shown below diamond.
Mr Singh
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Structure and Bonding
Metals 1. A) Having a high melting and boiling point makes metals useful by allowing them to be used in situations where other things would burn or melt. B) Mercury is the main exception and has a low melting and boiling point, this makes mercury useful in liquid metal thermometers 2. A malleable metal is one that can be hammered into a certain shape or thickness, such as Gold 3. A) Use a machine to clamp the substance at each end then slowly pull the metal. But if the metal were to snap it may sent fragments around the room so a safety screen is needed. B) Keep the volume of metal and dimensions the same and keep the rate of pulling the same 4. Substance
Use
Copper
Used for Wiring
Lead
Used to keep out radiation
Aluminium
Used for aircraft
Gold
Used for jewellery
5. A) Metal
Property
Use
Copper
Conducts electricity
Household wiring
Lead
Stops All radiation
Radiation Protection
Aluminium
Strong and light
Aircraft shells
Gold
Unreactive and beautiful
Jewellery
B) A mixture of metals is called an alloy C) Mixing metals allows for the good properties of one to join with another. D) To make an alloy, one must mix molten metals. E) The atoms do not fuse and therefor it is a mixture not a compound
Mr Singh
39
Structure and Bonding
Fraser Duncumb
Friday, 26 August 2016
6. A) Tungsten has a very high melting point which means that it can be heated in argon to glow. 4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 00 Melting Point
Aluminium
B)
Copper
Gold
Iron
Lead
Tin
Tungsten
7. Metallic oxide are alkali compared to non-metallic oxides 8. Gold is unreactive and does not react with oxygen in the air and therefore cannot tarnish. Gold is found in the ground because it does not react with other substances in the ground so it does not form a compound naturally
Mr Singh
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Structure and Bonding
Nanoparticles This table shows some of the units used for measuring length. Each unit is 1000 times smaller than the one before Unit name Gigametre Megametre Kilometer Metre Millimetre Micrometre nanometre
Unit symbol Gm Mm km m mm Îźm nm
Meaning One billion metres One million metres One thousand metres One metre One thousandth of a metre One millionth of a metre One billionth of a metre
Nanoparticles range from about 100nm to about 1nm. They are the size of an individual particle and can only be seen through some highly sophisticated equipment. Uses of nanoparticles 1. They have a very high surface area compared to their volume so they can react very quickly. They are therefore excellent catalysts. 2. Nanoparticles have different properties from normal-sized pieces. 3. Nano sized titanium oxide is used in sun creams as it blocks UV light. Other uses being developed: 1. 2. 3. 4. 5.
New catalysts New coatings New computers Stronger and lighter building materials Sensors that detect individual substances in tiny amounts.
Mr Singh
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Structure and Bonding
Ionic Bonding Definition:
Draw the Dot Cross Diagrams for the following Ionic Compounds: 1. Sodium Chloride !"#$
2. Potassium Bromide !"#
3. Calcium Oxide!"#
4. Magnesium Chloride !"#!!
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Structure and Bonding
5. Aluminium Oxide !!! !!
6. Aluminium Chloride !"#!!
7. Potassium Oxide !! !
8. Lithium Nitride !"! !
Mr Singh
43
Structure and Bonding
Ionic Bonding 1. (a)
An atom of potassium has an atomic number of 19 and a mass number of 39. How many protons, electrons and neutrons are in this atom? Electrons
Protons
Neutrons
[3]
(b) What is the electron arrangement of this atom? __________________________________________________________[1] (c) What will a potassium atom want to do in its reactions to achieve a noble gas electron arrangement? __________________________________________________________[1] 2. A oxygen atom has an electron arrangement of 2,6. In reactions, oxygen likes to gain two electrons to form an oxide ion. (a) Why does an oxygen atom like to gain two electrons in reactions? _________________________________________________________[1] (b) What is the symbol and charge of an oxide ion? _________________________________________________________[1] (c) Why does an oxide ion have this charge? _________________________________________________________[1] 3. Give the symbol and charge of the following ions: (a)
sodium ion
___________
(b)
chloride ion __________
(e) copper(II) ion __________ (g)
(b) (d) (f)
aluminium ion _____________ hydrogen
ion _____________
carbonate ion ______________
ammonium ion _____________
[7]
4. What are the formulae of the following ionic compounds(the ions that these contain are given below): (a) lithium
Mr Singh
bromide
___________ (b)
lead(II) fluoride
___________
44
Structure and Bonding
(c) iron(III) sulphide ___________
(d)
(e)
(f) magnesium hydroxide___________[6]
tin(IV) nitrate ____________
potassium sulphite ___________
Li+
lithium
Br-
bromide
Pb 2+
lead(II)
F-
fluoride
Fe 3+
iron(III)
S 2-
sulphide
K+
potassium
SO3 2- sulphite
Sn 4+
tin (IV)
NO3 – nitrate
Mg 2+ magnesium
OH-
hydroxide
5. Draw the dot-cross diagram for the following two ionic compounds. Only the outer shells need be shown: (a)
sodium chloride, NaCl
(b) Lithium oxide, Li2O
The atomic numbers of sodium, chlorine, lithium and oxygen are 11, 17, 3 and 8 respectively. (a)
[2]
(b)
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Structure and Bonding
[2]
6. Magnesium oxide, MgO is a typical ionic compound with a giant ionic solid structure. It is used to make the heat resistant linings of industrial furnaces e.g for use in pottery making. (a) Why is there a strong attraction between magnesium and oxygen in this ionic compound? _________________________________________________________[1] (b) Give three physical properties that you would expect magnesium oxide to have as a typical giant ionic solid. __________________________________________________________ __________________________________________________________ _________________________________________________________[3]
Mr Singh
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Structure and Bonding
Molecules – Covalent Bonding Draw out the Dot Cross diagrams for the following molecules: a) Hydrogen
e) Carbon Dioxide
b) Chlorine
f) Water
c) Oxygen
g) Methane (!!! )
d) Nitrogen
h) Ethane (!! !! )
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47
Structure and Bonding
c) Ammonia (!!! )
h)
Hydrogen Fluoride (!")
d) Phosphine (!!! )
i)
Ethene (!! !! )
e) Silicane (!"!! )
j)
Hydrogen Nitrile (HCN)
f) Sulphur Dioxide (!!! )
k) Nitrogen Dioxide (!!! )
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Mr Singh
Propene
Name of MONOMER Ethene
Polychloroethene
Name of POLYMER
Displayed formula of the monomer
Displayed formula of the polymer showing three REPEAT UNITS
Use your understanding of polymerisation to complete the following table
Addition Polymerization Polymer formula
Structure and Bonding
49
J10.1
Metallic bonding Structure and Bonding
1 The electronic structures of some different metals are shown below. For each one, draw a diagram to show the metal atom, then draw it again to show what happens when it becomes an ion. The first one has been done for you. a) magnesium 2,8,2 2+
magnesium atom 2,8,2
magnesium ion [2,8]2+
b) lithium 2,1 c) aluminium 2,8,3 d) calcium 2,8,8,2 2 The box shows some characteristics of metallic bonding. There are strong forces holding the ions together. Layers of ions can slide over each other. The outer electrons can move around between the ions. Which characteristic(s) of metallic bonding explain: a) the strength of metals b) conduction of electricity c) conduction of heat d) malleability e) high melting and boiling points? 3 Metals are chosen for different purposes because of their properties. For example, saucepans are usually made of metal because metals are good conductors of heat and have high melting points. This means that they conduct heat quickly from the cooker to the food, and will not melt when they are heated. For each of the uses below, write down which properties of metals are useful, and explain why those properties are needed. a) electrical wires b) bridges c) radiators d) cars
Mr Singh Š Pearson Education Limited 2003
243
50 2 Longman Higher Science for GCSE
J
J1.2
States of matter Structure and Bonding
Water has three different states. Ice is the solid state of water, and steam is water in its gas state. What we normally call water is a liquid. All substances are either solids, liquids or gases. Ice, liquid water and steam are all made of the same kind of particle. The three states of water are very different, because of the way the water particles are arranged. In solids, the particles are held together in a fixed arrangement. There are strong forces between the particles, holding them together. The particles can vibrate, but they cannot move around.
If you hold a snowball in your hand for long enough, the ice will melt. The heat energy from your hand is transferred to the snowball, and makes the particles vibrate faster. Eventually they will have enough energy to break away from each other and form a liquid. The melting point of ice is 0 °C. The particles in a liquid can move around, but they are still very close to each other. There are still quite strong forces holding them together.
Some particles in water move fast enough to escape from the liquid and become a gas. This is called evaporation. If you heat the liquid, more particles have enough energy to escape and the water will evaporate faster. If it is hot enough, all the particles have enough energy to turn into a gas. When a liquid is evaporating as fast as possible, little bubbles of gas form inside the liquid, and the liquid boils. The boiling point of water is 100 °C. In a gas, the particles can move around freely. There are only weak forces between them. 1 2 3 4 5 6
What are the three states of matter? Describe the arrangement of particles in a solid. What happens to the particles in a solid when the solid melts? Explain why putting wet gloves on a radiator helps to dry them. Describe the arrangement of particles in a gas. a) What does melting point mean? b) What does boiling point mean? 7 If some petrol is spilled in a garage, it soon disappears. Describe what is happening to the particles, in as much detail as you can. 8 a) What are the properties of solids, liquids and gases? (e.g. How well do they flow? Can they change shape? Can they be squashed?) b) Explain these properties using ideas about the arrangement of particles and the forces between them. 9 Spilled petrol usually dries up a lot faster than a puddle of water. What does this tell you about the boiling points of the two liquids? Explain your answer.
Mr Singh Š Pearson Education Limited 2003
227
51 2 Longman Higher Science for GCSE
J
Structure and Bonding
Ionic substances 1)
a) Explain why ionic substances have high melting and boiling points.(2) b) Explain why ionic substances can conduct electricity when melted or dissolved. c) Explain why ionic substances cannot conduct electricity when solid.
2)
The diagram shows the ions in solid sodium chloride. Re-draw the diagram to show how the ions would be arranged if the sodium chloride was melted.
(2)
(2)
-
Cl ion +
Na ion
(2) 3)
4)
Write the formula of the following ionic compounds. a) calcium chloride
d) aluminium hydroxide
b) sodium oxide
e) potassium carbonate
c) magnesium sulphide
f) calcium nitrate
(6)
Complete the passage below using the following words: loses ions ionic protons negative electrons positive gains Atoms are neutral because they have the same number of ………………….. and ………………… . If atoms lose or gain electrons they become electrically charged and are called ………… (they are not atoms any more). If atoms gain electrons they become ……………….... ions, and if they lose electrons they become ………………… ions. When a metal reacts with a non-metal, the metal atoms …………….. electrons and the nonmetal atoms …………… electrons, forming an ……………….. compound. (8)
5)
a) Complete the table about the metals below (answer on the sheet).(10) Element Group number
N a
K
M g
C a
Al
Number of electrons in outer shell Number of electrons needed to lose to get full outer shell Number of electrons needed to gain to get full outer shell Charge on the ion it forms b) What do you notice about the Group number and the charge on the ions for metals? (1)
Mr Singh
52
Structure and Bonding
6)
a) Complete the table about the non-metals below (answer on the sheet). Element
Cl
Br
I
O
(10)
S
Group number Number of electrons in outer shell Number of electrons needed to lose to get full outer shell Number of electrons needed to gain to get full outer shell Charge on the ion it forms b) What do you notice about the Group number and the charge on the ions for non-metals? (1) 7)
a) What is the electron configuration of the following ions? i) Na+
ii) Ca2+
iii) S2-
iv) F- (4)
b) What do you think would be the charge on ions formed from the following elements? i) strontium (Sr)
Mr Singh
ii)
tin (Sn)
iii) astatine (At)
(3)
53
Structure and Bonding
513WS
Simple molecular substances 1)
a) Explain why simple molecular substances have low melting and boiling points. b) Explain why simple molecular substances cannot conduct electricity.
2)
The diagram shows some of the molecules in frozen methane (i.e. solid CH4). a) Re-draw the diagram to show how the particles would be arranged if the solid methane was turned into a liquid.
O O
H atom C atom
(3)
a) Complete the table about the non-metals below (answer on the sheet). Element
(1)
O
O
b) Re-draw the diagram to show how the particles would be arranged if the methane was turned into a gas.
3)
(2)
Cl
O
N
(12)
C
Group number No. of electrons in outer shell No. of electrons needed to lose to get full outerofshell No. electrons needed to gain to get full outerofshell No. covalent bonds it forms
b) Why do non-metals gain electrons rather than lose electrons to get a full outer shell? (1)
c) How do non-metals fill their outer shells when forming bonds with metals? (1) d) How do non-metals fill their outer shells when forming bonds with non-metals? e) What is a covalent bond?
Mr Singh
(1)
(2)
54
Structure and Bonding
GCSE Structure 08 Š RWGrime
26/08/16
Giant covalent substances 1)
a) Explain why giant covalent substances have very high melting and boiling points. (2) b) Explain why diamond is very hard (it is used for making very hard drill bits). c) Explain why graphite can conduct electricity.
(2)
(2)
d) Explain why most giant covalent substances cannot conduct electricity. (1) e) Explain why graphite is soft (it is used in pencils and rubs off onto the paper). 2)
(2)
The diagram shows part of the structure of diamond. Re-draw the diagram to show how the particles would be arranged if diamond was heated and turned into a gas. (2)
3)
Silicon dioxide, also known as silica, has a giant covalent structure with the formula SiO2. In your (2) own words, explain what the formula SiO2 tells you about silicon dioxide.
4)
a) What is the difference between a simple molecular substance and a giant covalent substance? (5) b) In 1985, a new form of carbon, besides diamond and graphite, was identified. It was made by the action of a laser on some graphite. It was called buckminsterfullerene after the American architect Buckminster Fuller who built buildings in complex geometric shapes. The shape of buckminsterfullerene is the same as footballs. It has the formula C60. Is it a simple molecular substance or a giant covalent substance (explain your answer)?
Mr Singh
(2)
55
Structure and Bonding
Uses of common metals You need to know about aluminium, copper, and iron. 1.
Match the heads to the correct tails, and write out the correct sentences: heads Aluminium is used for Copper is used for Iron is used for
tails water pipes and electrical wires bridges, manhole covers and gates aircraft and overhead electricity cables
2. Aluminium has these properties: It is shiny, non-toxic (not poisonous), low density (light for its size) and does not corrode (rust). a) Why is aluminium a good metal to use for drinks cans? b) Why is aluminium a good metal to use as a reflector in car headlights? c) Why is aluminium a good metal to use for the superstructure (top decks) of warships? 3. Copper has these properties: It is a good electrical conductor, a good heat conductor and does not corrode (rust). a) Why is copper a good metal to use for water pipes? b) Why is copper a good metal to use for pans? c) Why is copper a good metal to use for electrical wires? 4. Iron has these properties: It is a hard, strong, cheap and it corrodes (rusts). a) Why is iron a good metal to use for bridges? b) Why is iron a poor metal to use for water pipes? c) Why are many things that are made of iron disposable? 5. Metals are often mixed with other elements to make alloys. Steel is a mixture of iron and carbon. Bronze is a mixture of copper and tin. a) Why are steel and bronze called alloys? b) Cupronickel can be used to make coins. What two metals do you think are in cupronickel? What properties should cupronickel have so that it makes good coins? c) Duralumin is an alloy of aluminium and some other metals. It is used to make aircraft parts. What properties should Duralumin have so that it makes good aircraft parts?
Mr Singh
N-m05-14 (Text Š N. Saunders 2000) 56
Structure and Bonding
Pure Metal
Alloy
What is it?
Structure
Hard/soft & explanation
Usefulness
Steels – alloys of iron % Fe
%C
Properties
Uses
Pure iron
Iron from blast furnace
Low C steel
High C steel
© www.CHEMSHEETS.co.uk Mr Singh
20-May-14
Chemsheets GCSE 138 57
Mr Singh
Hardness
Electrical conductivity
Structure
Physical Properties
Diamond
Graphite
Giant Covalent Structures Silica
Structure and Bonding
58
Structure and Bonding
1)
Which type of structure do the following substances have? K2O
K
O2
CH2O
Ar
S8
Br2
Cr
FeI3
MgSO4
N2H4
ionic simple molecular metallic monatomic giant covalent
2)
Look at the properties of the following substances. Electrical conductivity as
Substance
Melting point (°C)
Boiling point (°C)
solid
liquid
A
587
843
does not conduct
conducts
B
28
201
does not conduct
does not conduct
C
-39
357
conducts
conducts
D
-189
-101
does not conduct
does not conduct
E
2157
2895
does not conduct
does not conduct
F
1024
1598
does not conduct
conducts
a) Which of these compounds could have an ionic structure? VVVVVVVVVVVVVVVVVVVVVVV b) Which of these compounds could have a simple molecular structure? VVVVVVVVVVVVVVVVVV. c) Which of these compounds could have a metallic structure? VVVVVVVVVVVVVVVVVVVVVV. d) Which of these compounds could have a giant covalent structure? ..VVVVVVVVVVVVVVVVVVV.
3)
Write the formula of the following ionic compounds. a) potassium oxide
VVVVVV
d) copper carbonate
VVVVVV
b) magnesium nitrate
VVVVVV
e) ammonium hydroxide
VVVVVV
f) iron (III) oxide
VVVVVV
c) aluminium hydroxide VVVVVV
4)
a) Aluminium is a metal. Explain why it has a high melting point. VVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV.. b) Explain why aluminium conducts electricity. VVVVVVVVVVVVVVVVVVVVVVVVVVVVVV. VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV..
© www.CHEMSHEETS.co.uk Mr Singh
09-July-13
Chemsheets GCSE 065 59
Structure and Bonding
5)
a) Aluminium oxide is an ionic substance with formula Al2O3. Explain what this formula means. ======== =================================================. =================================================. b) Explain why aluminium oxide has a high melting point. ========================.. =================================================. c) Explain why aluminium oxide does not conduct electricity as a solid but does when melted. ========... =================================================. =================================================.
6)
a) Ammonia is a simple molecular substance with formula NH3. Explain what this formula means. ======... =================================================. =================================================. b) Explain why ammonia has a low melting point. =======.=====..===============.. =================================================. c) Explain why ammonia does not conduct electricity in any state. ================.====... =================================================. =================================================.
7)
a) Explain why diamond is hard but graphite is soft. ============================ =================================================. =================================================. b) Explain why graphite conducts electricity but diamond does not. ===================== =================================================. =================================================.
8)
Complete the table to draw any missing stick or dot-cross diagrams for the molecules shown below. Substance
ammonia
NH3
oxygen
O2
oxygen fluoride OF2
H Stick diagram
H
N
H
Dot-cross diagram
Š www.CHEMSHEETS.co.uk Mr Singh
09-July-13
Chemsheets GCSE 065 60
Structure and Bonding
Think creatively
1. Summarise how ionic, covalent and metallic bonding works using in a cartoon. 2. Research and prepare a two minute presentation about a promising development in nanotechnology. Why do you think this will be an exciting development?
Mr Singh
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Structure and Bonding
Taking it further Why not find out more about the topic? Read the section of an A-level textbook from the library. Try and do some internet research to find out how we have come to view structures and bonding this way? What is the evidence for it? Read a book from the library or order it online: Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World, Mark Miodownik Molecules at an Exhibition: Portraits of Intriguing Materials in Everyday Life, John Emsley Radar, Hula Hoops, and Playful Pigs: 67 Digestible Commentaries on the Fascinating Chemistry of Everyday Life, Joe Schwarcz The Joy of Chemistry: The Amazing Science of Familiar Things, Cathy Cobb
Watch a free online documentary: Nano, the Next Dimension, BBC NanoTechnology Future of Technology The Strange World of Nanoscience, Nanoyou project
Mr Singh
62
Structure and Bonding
13
5 (c)
Sodium iodide can be produced from kelp.
5 (c) (i)
How many electrons are in the outer shell of an iodine atom?
Do not write outside the box
(1 mark) 5 (c) (ii) Sodium iodide contains sodium ions (Na+) and iodide ions (I–). Describe, as fully as you can, what happens when sodium atoms react with iodine atoms to produce sodium iodide. You may use a diagram in your answer
............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (3 marks)
Question 5 continues on the next page
Turn over Mr Singh (13)
63 G/J89668/Jan13/CH2HP
Structure and Bonding
15
6
Do not write outside the box
Silicon dioxide is used as a lining for furnaces. Furnaces can be used to melt iron for recycling.
The diagram shows a small part of the structure of silicon dioxide.
Key Oxygen atom Silicon atom
Explain why silicon dioxide is a suitable material for lining furnaces. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (4 marks)
____ 4 Turn over Mr Singh (15)
64 G/J89668/Jan13/CH2HP
Structure and Bonding
16
7
Do not write outside the box
Etching is a way of making printed circuit boards for computers.
Printed circuit boards are made when copper sheets are etched using iron(III) chloride solution. Where the copper has been etched, only plastic remains. 7 (a)
Copper is a good conductor of electricity. Explain why. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (2 marks)
Mr Singh (16)
65 G/J89668/Jan13/CH2HP
Structure and Bonding
501P
Sodium Chloride - Practical The aim of this practical is to look at the general properties of sodium chloride. 1. Heat some sodium chloride crystals (take a heaped spatula full) strongly in a boiling tube. • •
What happens? Why do you think this happens?
2. Add 2 spatulas of sodium chloride to half a beaker of water and stir. •
What is happening to the crystals and the particles within the crystals?
3. Using the beaker from experiment 2, place two electrodes (connected to an electrical circuit of 6V DC) into the solution. • What can you see happening? • Is a current flowing?
4. Now test a dry sample of solid sodium chloride using dry electrodes in the same way as in experiment 3. • What can you see happening? • Is a current flowing?
Mr Singh
66
Structure and Bonding
502P
Heating Sulfur – Practical The aim of this practical is to see the properties and appearance of a substance can change as different types of bonds are broken and formed Collect 3 spatulas of powdered sulphur in a test tube. Warm it gently over a Bunsen flame What happens? Describe the changes that you see When it has melted, heat the sulphur more strongly. Keep the flame away from the mouth of the test tube to make sure that any sulphur vapour escaping doesn’t catch fire. When the liquid is about to boil, pour the molten sulphur into a beaker of cold water. Leave it under water for 30 seconds and then pick out the lump with your fingers. Describe the changes you notice.
Sulfur exists as S8 molecules at room temperature. These crown-shaped molecules are packed neatly together to form crystals. It melts at 115 °C. This low melting point tells us that sulfur has a simple molecular structure. There are relatively weak forces between its molecules As the molten sulfur is heated more strongly, the rings of S8 sulfur atoms open up. They then join together to make long chains. Near its boiling point the long chains start to break up. They escape from the liquid as a gas. If you pour the molten sulfur into cold water, plastic sulfur is made. The sulfur does not have time to change back into its S8 molecules. It is frozen’ in a long chain structure, like rubber. Eventually the plastic sulfur goes hard. It changes back slowly into S8 molecules again.
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Structure and Bonding
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68