GCSE workbook Atomic Structure
Contents 1. Specification 2. Helping yourself 3. Pre-topic test 4. Record of Comments and Targets 5. Notes 4.1.1 A Simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes 4.1.2 The Periodic Table 4.1.3 Properties of Transition metals 6. Questions 7. Taking it further 8. Revision questions 9. Practicals
4.1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes 4.1.1.1 Atoms, elements and compounds Content
Key opportunities for skills development
All substances are made of atoms. An atom is the smallest part of an element that can exist. Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium. There are about 100 different elements. Elements are shown in the periodic table. Compounds are formed from elements by chemical reactions. Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change. Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed. Compounds can only be separated into elements by chemical reactions. Chemical reactions can be represented by word equations or equations using symbols and formulae. Students will be supplied with a periodic table for the exam and should be able to: • use the names and symbols of the first 20 elements in the periodic table, the elements in Groups 1 and 7, and other elements in this specification • name compounds of these elements from given formulae or symbol equations • write word equations for the reactions in this specification • write formulae and balanced chemical equations for the reactions in this specification. (HT only) write balanced half equations and ionic equations where appropriate.
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016
4.1.1.2 Mixtures Content
Key opportunities for skills development
A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.
WS 2.2, 2.3 AT 4
Safe use of a range of Mixtures can be separated by physical processes such as filtration, equipment to separate crystallisation, simple distillation, fractional distillation and chemical mixtures. chromatography. These physical processes do not involve chemical reactions and no new substances are made. Students should be able to: • describe, explain and give examples of the specified processes of separation • suggest suitable separation and purification techniques for mixtures when given appropriate information.
4.1.1.3 The development of the model of the atom (common content with physics) Content
Key opportunities for skills development
New experimental evidence may lead to a scientific model being changed or replaced.
WS 1.1, 1.6
Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided. The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it.
This historical context provides an opportunity for students to show an understanding of why and describe how scientific methods and theories develop over time.
The results from the alpha particle scattering experiment led to the WS 1.2 conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model. Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations. Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles. The experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. This was about 20 years after the nucleus became an accepted scientific idea. Students should be able to describe:
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Content
Key opportunities for skills development
• why the new evidence from the scattering experiment led to a change in the atomic model
WS 1.1
• the difference between the plum pudding model of the atom and the nuclear model of the atom.
WS 1.2
Details of experimental work supporting the Bohr model are not required. Details of Chadwick’s experimental work are not required.
4.1.1.4 Relative electrical charges of subatomic particles Content
Key opportunities for skills development
The relative electrical charges of the particles in atoms are:
In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge. The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons. Students should be able to use the nuclear model to describe atoms.
WS 1.2
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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016
4.1.1.5 Size and mass of atoms Content
Key opportunities for skills development
Atoms are very small, having a radius of about 0.1 nm (1 x 10-10 m). WS 4.3, 4 The radius of a nucleus is less than 1/10 000 of that of the atom (about 1 x 10-14 m).
Use SI units and the prefix nano.
Almost all of the mass of an atom is in the nucleus.
MS 1b
The relative masses of protons, neutrons and electrons are:
Recognise expressions in standard form.
The sum of the protons and neutrons in an atom is its mass number. Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element. Atoms can be represented as shown in this example:
Students should be able to calculate the numbers of protons, neutrons and electrons in an atom or ion, given its atomic number and mass number. Students should be able to relate size and scale of atoms to objects MS 1d in the physical world.
4.1.1.6 Relative atomic mass Key opportunities for skills development
Content
The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element. Students should be able to calculate the relative atomic mass of an element given the percentage abundance of its isotopes.
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4.1.1.7 Electronic structure Content
Key opportunities for skills development
The electrons in an atom occupy the lowest available energy levels WS 1.2 (innermost available shells). The electronic structure of an atom can Students should be able to be represented by numbers or by a diagram. For example, the represent the electronic electronic structure of sodium is 2,8,1 or structures of the first twenty elements of the periodic table in both forms. MS 5b
showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level.
Visualise and represent 2D and 3D forms including twodimensional representations of 3D objects.
Students may answer questions in terms of either energy levels or shells.
4.1.2 The periodic table 4.1.2.1 The periodic table Content
Key opportunities for skills development
The elements in the periodic table are arranged in order of atomic (proton) number and so that elements with similar properties are in columns, known as groups. The table is called a periodic table because similar properties occur at regular intervals. Elements in the same group in the periodic table have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties. Students should be able to:
WS 1.2
• explain how the position of an element in the periodic table is related to the arrangement of electrons in its atoms and hence to its atomic number • predict possible reactions and probable reactivity of elements from their positions in the periodic table.
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Helping yourself Read the section on Atomic structure and the Periodic table in your textbook Read the relevant sections of these websites bbc.co.uk/schools/gcsebitesize/chemistry gcsescience.com docbrown.info revisioncentre.co.uk youtube for video tutorials other teachers!
Elements Everything around us is made up of atoms. Atoms are very tiny particles; there would be a hundred million atoms across the centre of a penny. There are 92 different types of atoms that occur naturally. A substance which is made up of only one type of atom is called an element. So there are 92 natural elements. Definition of “element� An ELEMENT is a substance made from only one type of atom. This means that it cannot be broken down into two or more simple substances by means of a chemical reaction.
Iron
Fe
Chlorine
Cl2
Oxygen
O2
Elements are divided into two classes - metals and non-metals.
Physical and Chemical Properties of Metals
7) HIGH DENSITY
6) SHINY
1) FORM BASIC OXIDES (ALKALINE IF SOLUBLE IN WATER)
2) HIGH MELTING POINT
METALS
3) MALLEABLE and DUCTILE
5) GOOD CONDUCTORS OF ELECTRICITY
4) GOOD CONDUCTORS OF HEAT
Physical and Chemical Properties of Non-Metals 1) FORM ACIDIC OXIDES 7) LOW DENSITY
6) DULL
5) POOR CONDUCTORS OF ELECTRICITY
NON-METALS
2) LOW MELTING POINT
3) BRITTLE
4) POOR CONDUCTORS OF HEAT
The Periodic Table The Basic Arrangement The Periodic Table is a way of presenting the elements in a systematic way. When the elements are placed in order of their atomic number and their properties looked at, a pattern can be seen. H 1
He 4
Li 7
Be 9
B 11
C 12
N 14
O 16
Reactive metals gases
F 19
Ne 20
Na 23
M g 24
Al 27
Si 28
Reactive non-metals
P 31
S 32
Cl 35
Ar 40
K 39
Ca 40
Unreactive
The elements with similar properties are then placed in the same column.
H 1
He 2
Li 3
Be 4
B 5
C 6
N 7
O 8
F 9
Ne 10
Na 11
Mg 12
Al 13
Si 14
P 15
S 16
Cl 17
Ar 18
K 19
Ca 20
Groups and Periods The columns in the Periodic Table are called groups The rows in the Periodic Table are called periods.
Period 1 Period 2 Period 3 Period 4 Period 5 Group 1 Group 2
3 4 5 6 7 8
Metals and Non-metals In the Periodic Table the metals appear on the left and the non-metals on the right.
H Li Na K Rb Cs
Be Mg Ca Sc Sr Y Ba La
Metals
Ti Zr Hf
V Cr Mn Fe Nb Mo Tc Ru Ta W Re Os
Co Rh Ir
Ni Pd Pt
B Al Cu Zn Ga Ag Cd In Au Hg Tl
C Si Ge Sn Pb
N P As Sb Bi
Non-metals
Atomic Structure and the Periodic Table The number of electrons in the outer energy level is the same as the group number of the element in the Periodic Table. e.g. Group 1 Li 2:1 Na 2:8:1 K 2:8:8:1 Similarly elements in group 3 always have three electrons, and elements in group 7 have seven electrons in their outer energy level. The number of electron energy levels is the same as the period number of the element in the Periodic Table.
O S Se Te Po
F Cl Br I At
He Ne Ar Xe Kr Rn
Elements, Compounds and Mixtures An ELEMENT is a substance made from only one type of atom. This means that it cannot be broken down into two or more simple substances by means of a chemical reaction. A COMPOUND is a pure substance made of different types of atom that have been chemically joined together in a fixed proportion. A MIXTURE is made of at least two substances together that have not been chemically combined. If we know that a “substance” contains certain elements, it may be difficult to decide whether these are just mixed together – as in air – or combined, as in copper sulphate crystals. To help decide, we may consider the following.
Compounds 1
Proportions of elements are fixed.
2
Properties different from those of the elements used to make the compound. Cannot be separated into elements without a chemical reaction.
3
4
There is usually a significant energy change when a compound is made from its elements.
Mixtures Proportions of the different substances may vary. Properties are those of the separate substances in the mixture. Can be separated by a physical change (e.g. dissolving one of the substances) or by a simple method (e.g. using a magnet to separate iron). There is usually no significant energy change when substances are mixed.
e.g. Hydrogen and oxygen combine to form water. Water is a compound. It is not easy to separate water into hydrogen and oxygen. Sodium and chlorine combine to form sodium chloride or salt. Salt is a compound. Salt dissolves in water to form salt solution. This is an example of a mixture. When salt solution is heated, or left for some time, the water evaporates leaving the salt. So this mixture can be separated again fairly easily.
Molecules When atoms join together, the group of combined atoms is called a molecule. Molecules may contain atoms of the same type or of different types. • When molecules contain atoms of the same type – these are molecules of an element. • When molecules contain atoms of different type – these are molecules of a compound.
Examples of elements, mixtures and compounds
Methane is a compound
Water is a compound of oxygen
of carbon and hydrogen
and hydrogen.
This shows a mixture of an element (oxygen) and a compound (methane).
This shows a mixture of two elements, hydrogen and chlorine.
This shows a mixture of two compounds, water and methane.
3rd Form notes
Types of Mixtures Matter can be divided into three types. Elements, Compounds and Mixtures. An Element is a chemical substance which cannot be broken down into anything simpler by chemical means. Or, a substance which is made up of only one kind of atom. A Compound is a single substance made from a specific combination of two or more elements in fixed proportions. Or, a compound contains atoms of different elements chemically joined together. A Mixture contains more than one substance which are not chemically combined.
3rd Form notes
Types of Mixtures: 1. SOLIDS and LIQUIDS A) Solutions Solutions are the result of a solid completely dissolving in a liquid. We say the solid is Soluble in the liquid. The liquid is called the Solvent and the solid is called the Solute. Together they form a Solution. They have not reacted as the particles are still separate but they have broken up to be so small, solutions appear clear.
Figure 1 Solute + Solvent => Solution
Tea is a mixture of water and other substances (solids in liquid) B) Suspensions Sometimes a mixture of a solid and a liquid doesn’t dissolve, we say it is Insoluble and so it forms a Suspension. In a suspension the particles of the solid don’t break up but cluster so the solid can still be seen. Suspensions are opaque, you cannot see through them. The solid after time settles to the bottle as Sediment.
Figure 2 A suspension
Chalk in water is an example of a Suspension (Solid and Water)
3rd Form notes A suspension which doesn’t separate is called a Sol or Colloidal Solution. E.g Blood or ink.
Figure 3 Differences between a solution and suspension Figure 4 Names given to how a suspension may separate
2. LIQUIDS and LIQUIDS A) Miscible Liquids When two liquids mix completely they are either said to be Miscible and a clear solution is formed. Anything which is miscible in water we call an Aqueous solution.
Wine is a mixture of two miscible liquids Water and Ethanol B) Immiscible liquids When two liquids don’t mix they are said to be Immiscible. When shaken vigorously the temporarily disperse in each other to form an Emulsion.
Milk is a Suspension of fat and water (solid and liquid)
3. SOLIDS and SOLIDS Solids can be mixed together to form mixtures. e.g. soil. Mixtures of two or more metals are called Alloys.
3rd Form notes
A 50p coin is a mixture of Copper and Nickel (solid and solid) 4. GASES and GASES Air is a mixture of many gases.
5. GASES with Solids and Liquids Small amounts of gas can dissolve in a liquid to form a Solution. E.g. carbonated water
Carbonated drinks area mixture of Water and Carbon dioxide (Liquid and a Gas) Large amount of Gases can be interspersed in a small amount of liquid to form an Aerosol or Foam
Shaving Foam is an Foam
Deodorants are Aerosols
Small particulates of solids can also be mixed in a gas which forms an Aerosol.
Smoke particles are an Aerosol of solid material suspended in air.
Separating Mixtures with Solids The method uses to separate a mixture depends on the physical state of the substances in the mixture. A. Separate a Solid from a Liquid 1. Filtration A Suspension (Solid is a liquid) with heavy sediment can be separated by Filtration. The solid left in the filter paper is called the Residue. The liquid gone through the filter paper is called the Filtrate. The process can be used for large amounts of suspension Figure 1 Filtration
2. Centrifuging A Suspension (Solid in a liquid) with a fine sediment or a Precipitate or Sol can be separated by Centrifuging. In a centrifuge the suspension is spun around very quickly causing the heavier solid particles to settle to be compacted at the bottom. The Supernatant Liquid can then be Decanted to leave the Figure 2 Centrifuging
solid which can then be washed and dried.
3. Evaporation of Solvent A Solution containing a solid and a liquid cannot be separated by the above methods because the particles are too small. The solution must be heated so that all the Solvent evaporates leaving the Solute behind.
Figure 3 Evaporation of Solvent to leave Solute
4. Crystallizing You can also separate Solutes from Solvents by letting the Solute crystallize as the solution slowly cools down reducing the saturation point of the solvent.
Figure 4 Leaving a hot solution to cool
B. Separate a mixture of two solids 1.
Dissolving If one of the solids is soluble you could dissolve the mixture in water, heat and stir to increase the rate of solubility and then decant off the hot solution leaving behind the insoluble solid or filter. Solvents usually include water, alkalis or acids or polar or non-polar organic solvents.
Figure 5 Dissolving in a solvent and filtering
2. Magnetism If one of the solids is magnetic then the two solids can be separated using magnets. This is usually only useful is one of the solids is Iron.
Figure 6 Using a magnet
Separating Mixtures containing Liquids Mixtures with liquids require different methods depending on whether they are miscible or immiscible. A. Solvent from a Solution Simple Distillation This is the way of getting a pure Solvent from a Solution. The solution is heated in a flask causing the solvent to evaporate leaving behind the solute. The vapour rises into the condenser where it comes into contact with water cooled glass causing it to condense. The condensed solvent runs off into the beaker to be collected. B. Miscible Liquids Fractional Distillation When two or more liquids are miscible they can be separated according to their different boiling points. The mixture is heated and the liquid with the lowest boiling point evaporated first. It then passes up the column heating them up and causing the liquid to condense back into the flask When beads are at the correct temperature all the way up the vapour with the lowest boiling point will go all the way up to the top without condensing and enter the condenser.
Here it will come into contact with the water cooled glass, condenses and runs into the second flask to be collected. The liquid with the higher boiling point will simple condense and fall back down. Once all of the first liquid has been evaporated off, the next vapour will warm up the bead enough that it can also escape out the top of the column.
C. Two Immiscible Liquids Separating Funnel The less dense liquids will always float on top of the more dense liquid and the bottom one can be tapped off through the bottom/
D. Separating a mixtures of coloured substances a. Chromatography This method is used to separate a mixture of coloured substances.
Each substance in the mixture will migrate at a different rate up the chromatography paper because they have different attractions for both the paper (the stationery phase) and the solvent (the mobile phase).
What remains at the end is called the Chromatogram.
The Rx value or Retention Value can also be calculated to help identify compounds. This is the ratio of the distance a substance travelled up the paper to the distance the solvent travelled. !! =
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A small concentrated sample of the mixture is places on some chromatography paper and some possible components are placed on the same level next to it. The paper is placed in a solvent so that the solvent travels up the paper drawing the different components up at different rates. After some time the paper is removed from the solvent and allowed to dry,
Writing Chemical Formulae Common Ions +1 Li+ Na+ K+ Ag+
+2 Mg2+ Ca2+ Zn2+
+3 Al3+
-3 N3-
-2 O2S2-
-1 FClBrI-
Questions Write the chemical formulae for the following compounds: 1. Sodium chloride
2. Calcium oxide
3. Zinc bromide
4. Aluminium oxide
5. Potassium nitride
6. Aluminium fluoride
Transition metal ions Transition elements can form different positive ions. To find out what type of positive ion we write a roman numeral between the metal and non-metal in the compound
E.g.
Copper(I) oxide
=
Cu2O
Copper(II) oxide
=
CuO
Copper(I)
=
Cu+
Copper(II)
=
Cu2+
Questions Write the chemical formulae for the following compounds: 1. Copper(II) chloride
2. Iron(III) bromide
3. Manganese(IV) oxide
4. Cobalt(II) iodide
Non-metal molecular ions These are groups of elements that together are either positively or negatively charged particles.
Ammonium
NH4+
Sulphate
SO42-
Nitrate
NO3-
Hydroxide
OH-
Carbonate
CO32-
Phosphate
PO43-
Sulphite
SO32-
Hydrogencarbonate HCO3-
Questions Write the chemical formulae for the following compounds: 1. Sodium hydroxide
2. Ammonium chloride
3. Calcium carbonate
4. Lead(II) sulphite
5. Copper(II) sulphate
6. Lithium hydrogencarbonate
7. Magnesium hydrogencarbonate
8. Iron(II) nitrate
9. Cobalt(II) hydroxide
Name: Balancing Chemical Equations In a chemical reaction, no atoms are created or destroyed. The same atoms that were in the reactant(s) must all appear in the product(s). More specifically, the number of atoms of each element on one side of a chemical equation must equal the number of atoms of that element on the other side. When this condition is met, the equation is BALANCED. Understanding the numbers in chemical equations: • Small numbers to the lower right of chemical symbols in a formula are called subscripts; this number indicates the specific number of atoms of that element found in one molecule of the compound.
H2O Subscript **Note: a molecule contains two or more atoms and is the smallest particle of a substance (element or compound) that retains all the properties of the substance. For example, 1 water molecule contains 2 hydrogen atoms and 1 oxygen atom. If you remove any of these components, the substance is no longer water.
• Big numbers in front of chemical formulas are called coefficients; this number applies to every element within the compound.
6CO2
Coefficient The coefficient indicates that there are ______ carbons atoms and ______ oxygen atoms in 6 molecules of carbon dioxide.
•
Subscripts of 1 are not written but understood (you don’t write H2O1; instead you write H2O).
Practice Problem: Is the following equation balanced? Yes or no.
C3H6
+
3O2
à
3CO2
+
3H2O
C = C = H = H = O = O = Rules for balancing equations: 1. Balance the elements one at a time by changing the coefficients in front of reactants and products. When no coefficient is written, it is assumed to be 1. 2. You may NOT change the subscripts in the chemical formula of a substance when trying to balance an equation. *Note: Pick an element to balance first and work through the elements in the equation one by one. It is best to begin with an element other than hydrogen or oxygen. These two elements often occur more than twice in an equation. 3. Finally, your coefficients must be in their smallest whole number ratio for the equation to be properly balanced. Example: The numbers 2, 2, 4, and 6 are not in their smallest whole number ratio. The numbers 1, 1, 2, and 3 are. Practice: 1. P4 + O2 à P4O10 2. Na + O2 à Na2O 3. C5H12 + O2 à CO2 + H2O
History of Atom notes filled in.notebook
September 22, 2015
HISTORY OF THE ATOM Democritus (Greece, 400s BCE) Nature's basic particle = "atom" Based on Greek word meaning "indivisible"
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Aristotle (Greece, 300s BCE) Did NOT believe in atoms Ideas accepted for ~2000yrs "Aristotle Altemps Inv8575" by Copy of Lysippus Jastrow (2006).
John Dalton (England, early 1800s) “billiard ball” model Atomic Theory
1) All matter composed of atoms 2) All atoms of same element are identical.(not true..stay tuned for isotopes) Atoms of different elements are different.
1
History of Atom notes filled in.notebook
September 22, 2015
Atomic Theory (cont'd) 3) Atoms cannot be created, destroyed or subdivided. (not true...think fission/fusion, synthetic elements) 4) Atoms of different elements combine in simple wholenumber ratios to form compounds:
Ex:
H2O
not
H7.97O4.12
5) In chemical reactions, atoms are combined, separated, or rearranged.
WarmUp 9/22/15 How Big is an Atom??
Fold your strip of paper in half crosswise (hamburger style). Cut in half. Repeat until you cannot cut anymore. How many times did you make cuts? 11" = .2794 m...must cut in half 36 times to reach the diameter of an atom:
4.1 x 1012 m
2
History of Atom notes filled in.notebook
September 22, 2015
J.J. Thomson (England, late 1890s) Cathode Ray Tube (CRT) expts.: (watch the videoclip!)
Cathode ray was attracted to positive magnet **Atoms have negative particles...ELECTRONS Since atoms are neutral, must also have positive particles...PROTONS
J.J. Thomson
electrons
“Plum pudding” model
Electrons much less massive than atoms
>This and CRT results suggest protons
protons
3
History of Atom notes filled in.notebook
September 22, 2015
Rutherford (New Zealand, 1911) Gold foil experiment: Positive alpha particles emitted at high speeds Aimed at gold foil Expected to pass through, if atom is mostly empty space
Rutherford However, he was SHOCKED, when 1 in 8000 particles were deflected Atoms must have a very small, densely packed center of positive charge: NUCLEUS
"As if firing a gun at a tissue and the shell came back at you!" watch the video clip!
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History of Atom notes filled in.notebook
Electrons in large, empty space
September 22, 2015
Rutherford's Model: "Nuclear atom" Small, dense, positive nucleus +
If nucleus = marble, atom = football field
Chadwick (England 1932) Mass of protons not heavy enough to = mass of atom
Another particle with no charge gives mass to nucleus: NEUTRON
5
History of Atom notes filled in.notebook
September 22, 2015
Subatomic Particle Summary Particle
Actual Mass Symbol Mass (kg) Number
Electron 9.11x1031
0
e
Proton 1.67x1027
1
p+
Neutron 1.67x1027
1
n0
*Number and arrangment of es determine chemical behavior
6
Structure of the atom
An…………………………………………… is a chemical substance that cannot be broken down (decomposed) into any more simple substances. An element contains only one type of ………………………………. Atoms are the particles that elements are composed of. An atom contains a………………………………in its centre. An atom contains ……………………………………………… …………………………………………….
The protons and neutrons are found in the nucleus. The electrons orbit in shells outside the nucleus. ……………………………… have a +1 charge and have about the same mass as a ……………………………… atom. The symbol for a proton is p+. ……………………………… have no charge as they are neutral. They have about the same mass as a ………………………………. The symbol for a neutron is n. ………………………………have a –1 charge and are 1840 times lighter than a proton or neutron. The symbol for an electron is e-. As an atom must be ……………………………… overall, the number of protons must be the same as the number of electrons.
The atomic number is the ………………………………………………………………. So if you know the atomic number, you also know the number of electrons in the atom as well as the proton number. Each element has its own different atomic number. Elements are organised in the Periodic Table by increasing atomic number. The mass number is the ………………………………………………………………If you subtract the atomic number from the mass number, you get the number neutrons. So, let us look at a helium atom. It has an atomic number of 2 and a mass number of 4. This means that there are 2 protons, 2 electrons and 2 neutrons in the atom: The electrons are arranged in ……………………………………………………or shells around the nucleus and with increasing distance from the nucleus. Each electron in an atom is in a particular ……………………………… ……………………………… (or shell) and the electrons must occupy the lowest available energy level (or shell) available nearest the nucleus. When the level is full, the next electron goes into the next highest level (shell) available. There are rules about the maximum number of electrons allowed in each shell and you have to be able to work out the arrangements for the first 20 elements.
The 1st shell has a maximum of 2 electrons. The 2nd shell has a maximum of 8 electrons The 3rd shell has a maximum of 8 electrons .
Appreciate the importance of the noble gas electronic configurations •
He = 2
•
Ne = 2,8
•
Ar = 2,8,8
•
Kr = 2,8,18,8
•
Xe = 2,8,18,18,8
In chemical reactions, atoms try to get the electron arrangement of the nearest ……………………………………………………………….
Isotopes An element is a substance that is made of only one kind of atom. There are over 105 different known elements of which 90 are naturally occurring. Every element has its own …………… and has a unique number of ………………... The number of protons an atom has is called the …………………….. Number or the Proton Number. In a neutral atom it is also the number of ………………… that the atom has. The protons are located in the ………………… of the atom along with the neutrons and the electrons orbit around the nucleus.
The Mass number of an atom tells us how massive an atom is and because electrons are relatively mass less, the mass number tells us the number of ……………….. and neutrons. The number of protons is always the same for every element but atoms of elements can have different numbers of Neutrons. Two atoms of the same element with different numbers of neutrons are called …………………. They exist naturally in different relative abundances. Isotopes are atoms of elements with the same number of protons but different number of neutrons. Examples: Carbon has three Isotopes
Hydrogen also has three isotopes:
Helium has two naturally occurring isotopes:
Relative Atomic Mass A single atom is very very light, about 0.000,000,000,000,000,000,000,002g. As these sorts of numbers are very awkward to use, we use ………………. mass units. (amu) The standard to which everything is compared has been decided to be 1/12th the mass of a Carbon-12 atom. This is because is almost the size of an Hydrogen atom, the smallest atom in the universe. The masses of all other atoms are therefore compared to this. We called this it’s Relative Atomic Mass. Element Hydrogen Carbon Nitrogen Oxygen Sodium Magnesium Sulfur
Symbol H C N O Na Mg S
RAM 1 12 14 16 23 24 32
Element Chlorine Potassium Calcium Iron Copper Zinc Iodine
Symbol Cl K Ca Fe Cu Zn I
RAM 35.5 39 40 56 64 65 127
Some atoms have isotopes so the ……………………. Atomic Mass is the ‘mean’ or average mass. The isotopes are also in different natural abundances so it is also the ‘weighted’ or proportioned average mass. The Relative Atomic Mass is the weighted mean mass of an atom of an element compared to the mass of 1/12th the mass of an atom of Carbon-12.
We can calculate the Relative Atomic Mass (RAM or Ar) by summing all the Mass numbers for each isotope multiplied by its relative abundance.
!! =
[ !"## !"#$%& !" !"#$#%& 1 ! !"#$%&'" !"#$%&$'( + (!"## !"#$%& !" !"#$#%& 2 ! !"#$%&'" !"#$%&$'() + ⋯ ]
e.g Chlorine. Chlorine has two isotopes of 35 and 37 amu. Their natural abundance is 75% and 25% respectively. !"#$%&'" !"#$%& !"#! (!! ) = [35 Ă—
!" !""
] + [37 Ă—
!" !""
] = 35.5 amu
201WS
Elements, compounds and mixtures 1)
Decide whether each of the following substances is an element or a compound. H2
2)
Co
HF
H 2S
S8
C6H12O6
CO
(8)
Look at the diagrams below and decide whether each one represents the particles in an element, a compound or a mixture. Different colour atoms represent atoms of different elements. (6) 1
3)
Br2
2
3
4
5
6
The diagram below represents the particles in air. a) Is air an element, a mixture or a compound?
(1)
b) i) Give the formula of each of the substances shown in the air. ii) Give the formula of each of the substances shown that are elements. iii) Give the compounds.
formula
of
each
of
the
substances (10)
N
N
N N
N
N
shown
N
N
N N Ar
H O H
O O
N
N
N N
O O
N N
N N
O
O
C O V
O
N
N N
N
that
are
Separating Mixtures Worksheet 1. A mixture of copper sulphate solution and solid soot (insoluble in water) had to be separated. (a) Describe carefully how you would separate this mixture. Draw a labelled diagram of the process used. What is this technique called? [4] (b) Which of the two substances formed the residue in the process of separation? [1] (c) Which of the two substances formed the filtrate in the process of separation? [1] 2. Some sugar has to be dissolved in water. (a) Describe TWO methods of speeding up the rate of dissolving the sugar in the water. [2] (b) What is the solvent in this mixture?
[1]
(c) What is the solute in this mixture?
[1]
(d) What does the term ‘dissolving’ mean? [2] (e) What is the name given to the mixture which contains a solute dissolved in a solvent? [1] (f) What would happen to the sugar, after it had been dissolved in the water, if it was filtered? Explain your answer. [2]
Chemical formulae. Write the chemical formula of each of the following.
Name 1 2
Silver iodide Nitric acid
3
Copper carbonate
4
Iron (III) bromide
5
Iron(II) sulphate
6
Barium chloride
7
Potassium oxide
8
Ammonium sulphide
9
Silicon carbonate
10
Sodium oxide
11
Potassium hydrogencarbonate
12
Magnesium iodide
13
Ammonium carbonate
14
Aluminium oxide
15
Iron (III) sulphate
16
Iron (II) bromide
17
Strontium oxide
18
Rubidium nitride
19
Magnesium hydroxide
20
Lead (IV) oxide
Total out
of 20
Formula
206WS GCSE Equations 01 © RWGrime
25/08/16
Balancing equations 1 1) Ca +
H2O → Ca(OH)2 + H2
2) CO + O2 →
CO2
3) Ca + O2 →
CaO
4) Fe2O3 + HCl → FeCl3 + H2O
5) NH3 + H2SO4 → (NH4)2SO4
6) Al +
H2SO4 → Al2(SO4)3 +
H2
206WS
7) CaO + HCl → CaCl2 + H2O
8) NH3 + O2 → NO + H2O
9) Na2O + H2O → NaOH
10) Na2CO3 + HCl → NaCl + CO2 + H2O
11) Br2 + KI → KBr + I2
12) Ca(OH)2 + HNO3 → Ca(NO3)2 + H2O
206WS
13) Fe + H2O → Fe3O4 + H2
14) Pb3O4 + HNO3 → Pb(NO3)2 + PbO2 + H2O
15) Cu + HNO3 → Cu(NO3)2 + H2O + NO
16) HNO3 → NO2 + H2O + O2
Balancing equations 2 1)
Mg (solid) + HCl (solution) → MgCl2 (solution) + H2 (gas)
2)
CuCl2 (solution) + NaOH (solution) → Cu(OH)2 (solid) + NaCl (solution)
3)
P (solid) + Cl2 (gas) → PCl3 (solid)
4)
PCl3 (solid) + H2O (liquid) → P(OH)3 (solution) + HCl (solution)
5)
C3H8 (gas) + O2 (gas) → CO2 (gas) + H2O (gas)
6)
copper (solid) + oxygen (gas) → copper oxide (solid)
7)
potassium (solid) + water (liquid) → potassium hydroxide (solution) + hydrogen (gas)
8)
aluminium oxide (solid) + nitric acid (solution) → aluminium nitrate (solution) + water (liquid)
9)
sodium hydroxide (solution)
+ nitric acid (solution) →
sodium nitrate (solution) + water (liquid) 10)
magnesium (solid) + silver nitrate (solution) → magnesium nitrate (solution) + silver (solid)
11)
magnesium (solid) + carbon dioxide (gas) → magnesium oxide (solid) + carbon (solid)
12)
ammonia (gas) + oxygen (gas) → nitrogen (gas) + water (gas)
13)
K2Cr2O7 + H2SO4 + CH3CH2OH → Cr2(SO4)3 + H2O + CH3CHO + K2SO4
202WS
Basic atomic structure 1) a) What three particles are atoms made from? b) Which particles are in the nucleus?
(3) (2)
c) Explain why atoms are neutral even though they contain positive and negative particles. (2) 2) a) Define the atomic (or proton) number of an atom. b) Define the mass number of an atom.
(1) (1)
c) Using the mass number and atomic number of an atom: i) How do you work out the number of neutrons in an atom? (1) ii) How do you work out the number of electrons in an atom? (1) iii) How do you work out the number of protons in an atom? (1) 3)
Complete the table below about the structure of atoms.
Atom
40
(21)
Atomic Mass No. of No.of No. of Electro numbe numbe protons neutro electro n r r ns ns structur e
Ar
18
27
Al
13
9
19
4
5 17 1
18 0
4) a) What are isotopes? b) Explain why isotopes have the same chemical properties.
(2) (2)
Atomic Structure
Atomic Structure
1. Copy the table below into your book, then complete it.
Element hydrogen lithium
Symbol 1 1H 7 3 Li 16 8O
Atomic number 1
Atomic mass 1
13
27
1. Copy the table below into your book, then complete it.
Number of: protons neutrons electrons 1 0 1
argon 19
22 20
127 238 92
13
27
Number of: protons neutrons electrons 1 0 1
19 53
2. a) Neutral atoms must have the same number of electrons as protons. Explain why. b) Atomic mass is the number of protons added to the number of neutrons. For example, beryllium has 4 protons and 5 neutrons, and so its atomic mass is 9. Explain why the number of electrons is not included in the atomic mass.
Draw, or write, a revision summary about how you do this. Use the lithium atom 73 Li as your example.
Symbol 1 1H 7 3 Li 16 8O
Atomic mass 1
argon
U
3. You can use the symbol of an element to work out the numbers of protons, neutrons and electrons there are in its atom.
Element hydrogen lithium
Atomic number 1
22 20
127 238 92
53
U
2. a) Neutral atoms must have the same number of electrons as protons. Explain why. b) Atomic mass is the number of protons added to the number of neutrons. For example, beryllium has 4 protons and 5 neutrons, and so its atomic mass is 9. Explain why the number of electrons is not included in the atomic mass. 3. You can use the symbol of an element to work out the numbers of protons, neutrons and electrons there are in its atom. Draw, or write, a revision summary about how you do this. Use the lithium atom 73 Li as your example. N-m08-05 (Š Nigel Saunders 2000)
Relative Atomic Mass Calculate the average atomic masses. Round all answers to two decimal places. 1. What is the atomic mass of hafnium if, out of every 100 atoms, 5 have a mass of 176, 19 have a mass of 177, 27 have a mass of 178, 14 have a mass of 179, and 35 have a mass of 180.0?
2. Iodine is 80% 127I, 17% 126I, and 3% 128I. Calculate the average atomic mass of iodine.
3. Calculate the average atomic mass of gold with the 50% being gold-197 and 50% being gold-198.
4. Calculate the average atomic mass of lithium, which occurs as two isotopes that have the following atomic masses and abundances in nature: 6.017 u, 7.30% and 7.018 u, 92.70%.
5. Hydrogen is 99% 1H, 0.8% 2H, and 0.2% 3H. Calculate its average atomic mass.
Electron shells
J6.1
1 Copy and complete these diagrams of electron shells. The first one has been done for you. (Hint: you do not always need all the shells shown in the diagrams.) a
b
c
,
2,5
d
,
2,7
e
,
,
f
2,8,8
2,8,8,2
2 a) Which elements are shown by the diagrams in question 1? Choose the elements from the table on the right. b) Explain how you worked out your answers.
J
Element
3 There is something wrong with these two diagrams. Explain what is wrong with each diagram, and draw the correct versions.
4,4
Š Pearson Education Limited 2003
lithium nitrogen fluorine magnesium silicon sulphur argon calcium
Atomic number 3 7 9 12 14 16 18 20
1,3,4
236
Longman Higher Science for GCSE 2
Taking it further Look up the lives and research of key men and women involved in developing the atom and the periodic table. Rutherford, Bohr, Einstein, Marie-Currie, Schrodinger, Heisenberg. What were their contributions? Read about atomic orbitals in an A-level textbook in the library websites: periodicvideos.com chemguide.co.uk s-cool.co.uk alevelchem.com Book list: The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of Elements, Sam Kean Seven Elements that Changed the World, John Browne Periodic Tales: The Curious Lives of the Elements, Hugh Aldersey-Williams Nature’s Building Blocks: An A-Z Guide to the Elements, John Emsley The Periodic Table: Elements with Style!, Simon Basher The Elements: A Very Short Introduction, Philip Ball Documentaries: The Clash of the Titans, BBC, Jim Al-Khalili, 3 episodes Chemistry: A Volatile History, BBC, Jim Al-Khalili, 4 episodes Hunting the Elements of the Periodic Table, PBS America
Fundamental Ideas Revision Questions 20 Marks 1.
The diagram represents an atom. Choose words from the list to label the diagram. electron
ion
neutron
nucleus
proton (Total 3 marks)
2.
The two carbon atoms represented below are isotopes.
ISOTOPE 1. 14 6
(a)
C
ISOTOPE 2. mass number
12
proton number
6
C
Describe two ways in which the isotopes are similar. ..................................................................................................................................... ..................................................................................................................................... (2)
(b) Describe as fully as you can one way in which they are different. ..................................................................................................................................... .....................................................................................................................................
Bradfield College
1
..................................................................................................................................... (2) (Total 4 marks)
3.
Atoms of calcium, phosphorus and fluorine are represented below, each with its mass number and proton number.
40
31 Ca
20
(a)
19 P
15
mass numbers F
proton numbers
9
Use this information to complete the table.
CALCIUM Number of protons in the nucleus
20
Number of neutrons in the nucleus
20
PHOSPHORUS
Number of electrons
FLUORINE 9
16 15
9 (3)
(b)
Calcium and fluorine atoms can combine to form the compound calcium fluoride, CaF2. The fluoride ion is represented by F–.
(i)
Explain how the fluorine atom forms a fluoride ion. .......................................................................................................................... .......................................................................................................................... (2)
(ii)
How is the calcium ion represented? .......................................................................................................................... (2)
(Total 7 marks)
4.
Electrons, neutrons and protons are sub-atomic particles.
Bradfield College
2
(a)
Complete the six spaces in the following table. Name of sub-atomic particle
Relative mass
Relative charge
.......................................
1
........................................
.......................................
........................................
0
.......................................
1 1840
......................................... (3)
(b)
An aluminium atom has 13 electrons. How are these arranged in shells around the nucleus? .................................................................................................................................... (1)
(c)
Chromium atoms have 24 protons and 28 neutrons. (i)
How many electrons does each neutral chromium atom have? ........................................................................................................................... (1)
(ii)
What is the mass number of chromium? ........................................................................................................................... (1)
(Total 6 marks)
Bradfield College
3
2
Do not write outside the box
Answer all questions in the spaces provided.
1
The Sun produces helium atoms from hydrogen atoms by nuclear fusion reactions.
Hydrogen
1 (a)
Helium
Describe the differences in the atomic structures of a hydrogen atom and a helium atom. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (3 marks)
(02)
G/J90872/Jan13/CH1HP
3 1 (b)
Do not write outside the box
The Sun consists of 73% hydrogen and 25% helium. The rest is other elements. One of the other elements in the Sun is neon. Use the Chemistry Data Sheet to help you to answer these questions.
1 (b) (i)
Complete the diagram to show the electronic structure of a neon atom.
(1 mark) 1 (b) (ii) Why is neon in the same group of the periodic table as helium? ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (1 mark)
____ 5
Turn over for the next question
Turn over
(03)
G/J90872/Jan13/CH1HP
3
Do not write outside the box
Answer all questions in the spaces provided.
1
The diagrams show the electronic structure of four different atoms.
Atom A
Atom B
Atom C
Atom D
Use the Chemistry Data Sheet to help you to answer these questions. 1 (a)
Name the two sub-atomic particles in the nucleus of an atom. ............................................................................................................................................ (1 mark)
1 (b)
Why is there no overall electrical charge on each atom? ............................................................................................................................................ ............................................................................................................................................ (1 mark)
1 (c)
Why is Atom A unreactive? ............................................................................................................................................ (1 mark)
1 (d)
Which two of these atoms have similar chemical properties? Give a reason for your answer. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (2 marks)
____ 5 Turn over
(03)
G/K84796/Jun12/CH1HP
2
Do not write outside the box
Answer all questions in the spaces provided. 1
This question is about atomic structure and elements.
1 (a)
Complete the sentences.
1 (a) (i)
The atomic number of an atom is the number of ............................................................ . [1 mark]
1 (a) (ii) The mass number of an atom is the number of ................................................................. .......................................................................................................................................... . [1 mark] 1 (b)
Explain why an atom has no overall charge. Use the relative electrical charges of sub-atomic particles in your explanation. [2 marks] ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................
1 (c)
Explain why fluorine and chlorine are in the same group of the periodic table. Give the electronic structures of fluorine and chlorine in your explanation. [2 marks] ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................
(02)
G/Jun15/CH1HP
3 1 (d)
Do not write outside the box
Figure 1 shows the electronic structure of an atom of a non-metal. Figure 1
Nucleus
What is the chemical symbol of this non-metal? [1 mark] Tick ( ) one box. Ar
O
S
Si
1 (e)
When elements react, their atoms join with other atoms to form compounds. Complete the sentences.
1 (e) (i)
Compounds formed when non-metals react with metals consist of particles called .................................................. . [1 mark]
1 (e) (ii) Compounds formed from only non-metals consist of particles called ........................................ . [1 mark] Turn over
(03)
G/Jun15/CH1HP
____ 9