How to Get Atomic Mass / Group 2 / Period 18/ Periodic Table
ELEMENTS
Electronegativity by Natalie Gilbert Atomic Radii? By Hemraj Polavoram Special Report: Trends of Periodic Table
“For me too, the periodic table was a passion. ... As a boy, I stood in front of the display for hours, thinking how wonderful it was that each of those metal foils and jars of gas had its own distinct personality.� - Freeman Dyson
ELEMENTS VOL. 180, NO. 5 2012
4/ Editor’s Desk
Period 2 17/ Period 2
6/ Introduc4on
18/ Mass Calcula4on 19/ Conference Review
7/ Introduc4on of Periodic Table Group 18 9/ Group 18 10/ Atomic Mass
I also taught myself how to blow glass using a propane torch from the hardware store and managed to make some elementary chemistry plumbing such as tees and small glass bulbs. ~Robert B. Laughlin
22/News More Trends in Period 2 Conclusion 23/ Conclusion
11/ Interview
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Editor’s Desk Introducing “The Periodic Table” Name: Natalie Gilbert Age: 16 School: Coppell High School
Name: Alice An Age: 16 School: Coppell High School
Name: Hemraj Polavaram Age: 16 School: Coppell High School 12/19/12
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Valence Electrons
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Introduction
In the Periodic Table of the Elements, all different kinds of Patterns or trends can be found. In this PBL, we are going to dig into the specific patterns found in Group 18 and Period 2.
Period 2: Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, Neon Group 18: Helium, Neon, Argon, Krypton, Xeon, Radon, Ununoctium 12/19/12
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Introduction of Periodic Table WHAT ARE THE GROUPS? The group number is an identifier used to describe the column of the standard periodic table in which the element appears. Groups 1-2 (except hydrogen) and 13-18 are termed main group elements. Groups 3-11 are termed transition elements. Transition elements are those whose atoms have an incomplete d-subshell or whose cations have an incomplete d-subshell. Main group elements in the first two rows of the table are called typical elements.
The following names for specific groups in the periodic table are in common use:
Group 1: alkali metals
Group 2: alkaline earth metals
Group 11: coinage metals (not an IUPAC approved name)
Group 15: pnictogens (not an IUPAC approved name)
Group 16: chalcogens
Group 17: halogens
Group 18: noble gases
Group 18
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Group 18
Group 18 Group 18 is considered as “Noble Gases”. In Group 18, Helium, Neon, Argon, Krypton, Xenon and Radon and Ununoc4um are included. The elements in the noble gases are reluctant to bond with other elements because they have a full electron shell. Krypton, Xenon, and Radon violate the octet rule when they force reacYvity and form compounds. Such compounds do exist, however, they are not common. Reports of compounds formed with Argon have been reported, but have not been confirmed, but Helium and Neon compounds are nonexistent. The reacYvity follows the order Ne < He < Ar < Kr < Xe < Rn. Examples of these compounds are KrF^2, XeF^4, and RnF^2.
Atomic Structure and Mass of Group 18
Element' Name' Helium' Neon' Argon' Krypton' Xenon' Radon' Ununoctium' !
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Symbol' He' Ne' Ar' Kr' Xe' Rn' Uuo'
#'of' protons' 2' 10' 18' 36' 54' 86' 118'
#'of' #'of' electrons' neutrons' Mass' 2' 2' 4.0026' 10' 10' 20.18' 18' 22' 39.948' 36' 48' 83.798' 54' 77' 131.29' 86' 136' 222.02' 118' 176' 294'
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Three isotopes of argon occur in nature – 36/18 Ar, 38/18 Ar, and 40/18 Ar. Calculate the average atomic mass of argon to two decimal places, given the following relaYve atomic masses and abundances of each of the isotopes: argon-‐36 (35.97 amu; 0.337%), argon-‐38 (37.96 amu; 0.063%), and argon-‐40 (39.96 amu; 99.600%). [(mass of isotope) (%abundance in decimal) ] + [(mass of isotope) (%abundance in decimal)] + [….] The equation continues on[….] based on the number of isotopes in the problem. (35.97 x 0.00337) +( 37.96 x 0.00063) + (39.96 x 0.99600) =
39.95 (amu).
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Interview Time!
Trends in Group 18: Noble Gas Family Alice An: Good morning! This is Alice An from Coppell High School. I am glad to have you all here today! We are going to talk about the trends of group 18 in the Periodic Table of Elements. Group 18 elements are called Noble Gases. Noble Gases are in state of gas at room temperature. Also, they are all non-‐metals because of the posiYon in Periodic Table. Ok, Let’s start talking! Hello, Hemraj and Natalie.
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Interview Hemraj: Hello, first of all, I am going to discuss about the trends of atomic radii and ionic radii. Ok. So look at this table that I have here…. On the very last column, it shows the atomic radius in picometer. As you can see by the info provided by the data table. The atomic radius increases in sporadic pakerns as you go down the group. Along with this, ionic radii also increase. It is fairly obvious that the atoms have larger masses as you go down groups. The reason is equally obvious-‐ you are adding extra layers of electrons. However, ionic radii have a lesser value digit than atomic radii.
Alice An: Cool! That is awesome! Well.. I want to know about reacYvity as well. Natalie, could you explain the reacYvity of group 18 please? Natalie: Ok, sure! It is very simple because group 18 elements are considered as noble gases, which do have full valence electrons thus, they don’t react to any elements. AddiYonally, some of the elements in Group 18 do not have any electronegaYvity as well. This is including Helium, Neon and Argon but Krypton, Xeon and Radon do bond to other substances so they form the compounds, which means, they do have the electronegaYvity. Alice An: Oh, that’s right! I remember learning about this when I was in Chemistry class. 12/19/12 Elements 12
Interview Natalie: All of the elements in Group 18 have similar electron configuraYon except helium. And due to that we can’t say that Group 18 elements have the same electron configuraYon. However, except Helium, all other noble gases have ns2np6 configuraYon. The electronic configuraYon of He is IS2. Due to this stable electronic configuraYon, they have fewer tendencies to take part of in chemical reacYons. He 1s^2 Ne 1s^2,2s^2,2p^6 Ar 1s^2,2s^2,2p^6,3s^2,3p^6 Kr [Ar] 4s^2,3d^10,4p^6 Xe [Kr] 5s^2,4d^10,5p^6 Rn [Xe] 6s^2,4f^14,5d^10,6p^6 Hemraj: The elements in Group 18, which we know as the inert or noble gases, each have a full outer electron shell. The fact that their outer shells are full means that they do not wish to either loan out or borrow electrons to complete their valence shells. As the loaning, borrowing or sharing of electrons to achieve fullness in the valence shell is the reason that elements react and form compounds with other atoms, the noble gases, because they have full valence shells, aren't generally interested in reacYng with other atoms of any kind. The reacYvity follows the order Ne < He < Ar < Kr < Xe < Rn. Alice An: Oh, so they have many common similariYes in elements of Group 18. Is there any pakern or trend that we can find more? Natalie: Well…. There are tons more. I can show you one more example. This concept is likle rare. IonizaYon energy is the energy needed to remove a valence electron from 1 mol of gaseous atoms. Group 18 elements have highest ionizaYon energy in their respecYve periods due to their stable noble gas configuraYon. Thus is one of the reasons for their less reacYvity. IonizaYon energy decreases on moving down the group due to increase in atomic size. The trends in IonizaYon energy are opposite those in atomic size. It is easier to remove an electron from a large atom than from a small one. 13 12/19/12 Elements
Interview
Alice An: Oh, IonizaYon energy… I didn’t know that there would be a trend about that. Well… I want to move onto the easy pakern. Could you please show me Lewis structure? Hemraj: Ok. I have prepared the Lewis structure for Group 18. As you can see, they all have full set of electrons, which are 8 valence electrons except Helium, which are 2 valence electrons. Lewis structure only shows the outer shell of electrons. Noble gases have the same amount of outer shell electrons. .
Natalie: Ok, I would like to talk about melYng point and boiling point as well. Noble gases’ boiling point and melYng point are preky lower than other elements. However, they increase as they go down the group. They are all in negaYve temperature as well as melYng point too. Also as you can see in the chart, the differences between boiling point and melYng point are preky low. There is not much gap between boiling point and melYng point
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Interview Hemraj: For the last pakern and addiYonal pakern that was not menYoned so far are atomic mass and atomic number. Atomic mass and atomic number increases as you move from top to bokom on the periodic table. Helium: # is 2, mass is 4.0026 Neon: # is 10, mass is 20.180 Argon: # is 18, mass is 39.948 Krypton: # is 36, mass is 83.798 Xenon: # is 54, mass is 131.29 Radon: # is 86, mass is 222.02 UnunocYum: # is 118, mas is 294 Alice An: Oh, that is right! We forgot about that!! Well… Thank you for coming out here and discussing about the Group 18 in Periodic Table! I really appreciate your work! We all got to know about Group 18 very well. Thank you again!
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Period 2
In Period 2, Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine and Neon are existed. Period 2 contains both metals and non-‐metals. Therefore, Period 2 is consisYng of all 4 makers, solid liquid gas and plasma because it goes across the table. Bonding: Chemical bonding between atoms of an element changes from metallic (Li & Be) to covalent in network structure (B & C) to covalent in individual molecules (N2, O2, & F2) to none in Ne. Bonding between each element and an acYve nonmetal (such as F2) changes from ionic to polar covalent, to nonpolar covalent. Lithium example: LiF -‐Tends to form with nonmetals/ionically(lose) Beryllium example: BeCl^2-‐ Tends to bond with nonmetals/ionically(lose) Boron example: BI^3(share) Carbon example: CO^2(gain) Nitrogen example: NBr^3(gain) Oxygen example:OF^2-‐ Tends to bond with nonmetals/ covalently(gain) Fluorine example:ClF-‐ Tends to bond ionically with low electronegaYvity metals (gain)
Atomic Structure of Period 2 Elements Element' Name' Lithium' Beryllium' Boron' Carbon' Nitrogen' Oxygen' Flourine' Neon'
Symbol' Li' Be' B' C' N' O' F' Ne'
#'of' protons'
#'of' electrons' 3' 4' 5' 6' 7' 8' 9' 10'
3' 4' 5' 6' 7' 8' 9' 10'
#'of' neutrons' 4' 5' 6' 6' 7' 8' 10' 10'
Mass' 6.94' 9.0122' 10.81' 12.011' 14.007' 15.999' 18.998' 20.18'
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How to Calculate an Atomic Mass for Boron?
[(mass of isotope) (%abundance in decimal) ] + [(mass of isotope) (%abundance in decimal)] + [….] The equaYon conYnues on[….] based on the number of isotopes in the problem. Example Boron The natural abundance for boron isotopes is: 19.9% 10B (10.013 amu) and 80.1% 11B (11.009amu). Calculate the atomic mass of boron. =[(.199)(10.013)] + [(.801)(11.009)] = 1.9926+8.8182 = 10.811 (amu) = 10.81 amu 12/19/12
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Conference Review
Recently, group of people from Chemistry class discovered the patterns shown in Periodic table for period 2. The conference was held in Coppell High School to hear the new discovery. During the conference, this table was provided for beker understanding.
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During the conference, three scienYsts, Natalie Gilbert, Hemraj Polavoram and Alice An were demonstraYng the trends that are found in elements of Period 2. First of all, they demonstrated the electronegaYvity trend. ElectronegaYvity was increasing from lev to right with the period.
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Atoms with low ionizaYon energies have low electronegaYviYes because their nuclei do not have a strong akracYon for electrons. Atoms with high ionizaYon energies have high electronegaYviYes because the nucleus has a strong akracYon for electrons. Therefore, IonizaYon energy increases from lev to right like the electronegaYviYes.
Electron configuraYon of valence shell changes from 2s1 through 2s2 2p6; number of electrons in the valence shell increases from 1 to 8. Thus, the electrons in Lewis Structure is added as it goes from lev to right. Li 1s^2,2s^1 Be 1s^2,2s^2 B 1s^2,2s^2,2p^1 C 1s^2,2s^2,2p^2 N 1s^2,2s^2,2p^3 O 1s^2,2s^2,2p^4 F 1s^2,2s^2,2p^5 Ne 1s^2,2s^2,2p^6
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Atomic size generally decreases with increasing effecYve nuclear charge; anomalous behavior is observed at Be and B (Be < B), and at N and O (N < O)
Ionic radii are difficult to measure with any degree of certainty, and vary according to the environment of the ion. Within the series of posiYve
ions, and the series of negaYve ions, that the ionic radii fall as you go across the period. However, in Period 2, Lithium and Beryllium who have
posiYve ions have the lowest radii but with negaYve ions, they have larger ionic radii. In order to compare the ionic radii, we need to look closely to posiYve ions and negaYve ions separately.
ReacYvity is highest on the lev end (for metal) and right end (for nonmetal), not including noble gas element of the period, and decreasing towards the middle.
Element Symbol
Boiling Point (C)
Mel4ng Point (C)
Li
1347
180.54
Be
2970
1278
B
2550
2300
C
4827
3500
N
-‐195.8
-‐209.9
O
-‐183
-‐218.4
F
-‐188.14
-‐219.62
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-‐246.1
-‐248.6 Elements
Their boiling points and melYng points are generally decreasing with non-‐metals because some of the elements are forms of gas, which have fairly lower boiling and melYng points. Carbon has the highest boiling point and melYng point. Metals and Metalloids are decreased with boiling points but increasing melYng points.
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The reducing strength decreases through the metals; oxidizing strength increases through the nonmetal (exclude noble gases).
The trend in physical properYes is such that it goes from sov and light metal with low melYng point (for Li) followed by a hard metal with high mp as occurs in beryllium to very hard metalloid with extremely high mp that occurs in boron. Then the nonmetals start with Carbon Atomic mass and atomic (middle of the period), the only number increases as you move from lev to right. nonmetal that is a solid. Important natural allotropes of carbon are Lithium: # is 3, mass is 6.94 graphite and diamond, which are Beryllium: # is 4, mass is physically very different. Graphite 9.0122 is opaque, sov and flaky, while Boron: # is 5, mass is 10.81 diamond in very hard and shiny. Carbon: # is 6, mass is 12.011 The other nonmetals (N2, O2, F2, Nitrogen: # is 7, mass is 14.007 and Ne) are all gases. Oxygen: # is 8, mass is 15.999 By… Hemraj Polavaram Fluorine: # is 9, mass is 18.998 Helium: # is 2, mass is 4.0026 12/19/12
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Conclusion The properYes of the elements show the enormous trends. These trends can be predicted using the Periodic Table of elements and can be understood by analyzing the electron configuraYons, which are very important for many pakerns because it is related to valence electrons of the elements. Elements tend to gain or lose valence electrons to achieve stable octet formaYon. Stable octets are seen in the inert gases, or noble gases, of the periodic table. First, electrons are added one at a Yme moving from lev to right across a period. As this happens, the electrons of the outermost shell experience increasingly strong nuclear akracYon with electronegaYviYes which affect the bonding, so the electrons become closer to the nucleus and more Yghtly bound to it. Second, moving down a column in the periodic table, the outermost electrons become less Yghtly bound to the nucleus. This happens because the number of filled the energy levels increases downward within each group. These trends explain the periodicity observed in the elemental properYes of atomic radius, ionizaYon energy, ionic radii, electronegaYvity, state of makers and other pakerns as well. The periodic table is one of the most important achievements in the field of chemistry. It is full of pakerns that enable us to beker understand the world around us. Without it, scienYsts would not have many of the products and medicine that we have today. The informaYon gained from the periodic table can open up numerous windows of knowledge about the enYre universe we live in. From this acYvity we realized and learned much more in depth understanding of the periodic table.
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"Chemical Elements.com -‐ An InteracYve Periodic Table of the Elements." Chemical Elements.com -‐ An Interac4ve Periodic Table of the Elements. N.p., n.d. Web. 18 Dec. 2012. <hkp://www.chemicalelements.com/index "General Chemistry II." Departmental Webpages. N.p., n.d. Web. 19 Dec. 2012. <hkp://departments.ozarks.edu/msc/che "Google Image Search Periodic Table."The Adventures of Accordion Guy in the 21st Century — Joey deVilla's Personal Blog. N.p., n.d. Web. 19 Dec. 2012. < hkp://www.joeydevilla.com/2006/09/21/google-‐image-‐search-‐periodic-‐table/>. " Periodic Trends in ElectronegaYvity | CK-‐12 FoundaYon ." Welcome to CK-‐12 Founda4on | CK-‐12 Founda4on . N.p., n.d. Web. 19 Dec. 2012. <hkp:// www.ck12.org/user:eWVvbWFubWlrZUBzYXlkZWwubmV0/secYon/Periodic-‐ Trends-‐in-‐ElectronegaYvity/>. "Physical Science Notes (info from the periodic table)." Lincoln Consolidated Schools. N.p., n.d. Web. 19 Dec. 2012. <hkp://web.lincoln.k12.mi.us/buildings/hs "VGA2WiFi Broadcasts Conference PresentaYons to Visually Impaired Akendees | SoluYons | Epiphan Systems." Screen Capture + Audio Video Capture, Encoding, Recording and Streaming Hardware | Epiphan Systems. N.p., n.d. Web. 19 Dec. 2012. <hkp://www.epiphan.com/soluYons_new/?arid=1080>. "2C.Directory.html." UC Davis: Student Academic Success Center. N.p., n.d. Web. 19 Dec. 2012. <hkp://lsc.ucdavis.edu/~ahart/Alicia2C/2
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