ELEMENTS How to Get Atomic Mass / Group 2 / Period 18/ Periodic Table

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  

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6/  Introduc4on  

7/  Introduc4on  of  Periodic  Table  

9/  Group  18  

10/  Atomic  Mass  

11/  Interview  

Group 18

Period 2

17/  Period  2  

18/  Mass  Calcula4on  

19/Conference  Review  

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  

23/Conclusion  

Conclusion

Editor’s Desk Introducing “The Periodic Table”

Name:  Alice  An  Age:  16  School:  Coppell  High  School  

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Name:  Natalie  Gilbert  Age:  16  School:  Coppell  High  School  

Name:  Hemraj  Polavaram  Age:  16  School:  Coppell  High  School  

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.

Group  18:  Helium,  Neon,  Argon,  Krypton,  Xeon,  Radon,  Ununoctium

Period  2:  Lithium,  Beryllium,  Boron,  Carbon,  Nitrogen,  Oxygen,  Fluorine,  

Neon  

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Introduction of Periodic Table

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.

WHAT ARE THE GROUPS?

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  

The following names for specific groups in the periodic table are in common use:

Group  18  

Period  2  

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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.    

Element'Name' Symbol'

#'of'protons'

#'of'electrons'

#'of'neutrons' Mass'

Helium' He' 2' 2' 2' 4.0026'Neon' Ne' 10' 10' 10' 20.18'Argon' Ar' 18' 18' 22' 39.948'Krypton' Kr' 36' 36' 48' 83.798'Xenon' Xe' 54' 54' 77' 131.29'Radon' Rn' 86' 86' 136' 222.02'Ununoctium' Uuo' 118' 118' 176' 294'!

Atomic Structure and Mass of Group 18

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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.    

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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.  

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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  

Interview

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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!    

Interview

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Period 2

Element'Name' Symbol'

#'of'protons'

#'of'electrons'

#'of'neutrons' Mass'

Lithium' Li' 3' 3' 4' 6.94'Beryllium' Be' 4' 4' 5' 9.0122'Boron' B' 5' 5' 6' 10.81'Carbon' C' 6' 6' 6' 12.011'Nitrogen' N' 7' 7' 7' 14.007'Oxygen' O' 8' 8' 8' 15.999'Flourine' F' 9' 9' 10' 18.998'Neon' Ne' 10' 10' 10' 20.18'!

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  

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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      

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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  

Ne   -­‐246.1   -­‐248.6  

 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  (middle  of  the  period),  the  only  nonmetal  that  is  a  solid.  Important  natural  allotropes  of  carbon  are  graphite  and  diamond,  which  are  physically  very  different.  Graphite  is  opaque,  sov  and  flaky,  while  diamond  in  very  hard  and  shiny.  The  other  nonmetals  (N2,  O2,  F2,  and  Ne)  are  all  gases.    By…  Hemraj  Polavaram  

   Lithium:  #  is  3,  mass  is  6.94  Beryllium:  #  is  4,  mass  is  9.0122  Boron:  #  is  5,  mass  is  10.81  Carbon:  #  is  6,  mass  is  12.011  Nitrogen:  #  is  7,  mass  is  14.007  Oxygen:  #  is  8,  mass  is  15.999  Fluorine:  #  is  9,  mass  is  18.998  Helium:  #  is  2,  mass  is  4.0026  

Atomic  mass  and  atomic  number  increases  as  you  move  from  lev  to  right.  

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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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