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CHEM 110 (151)
Lecture

Periodic table trends

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Department
Chemistry
Course
CHEM 110
Professor
Tomislav Friscic
Semester
Fall

Description
CHEM 110 NOTES 1: Periodic Table and trends Periodic  Law When  the  elements  are  arranged  by  atomic  mass,  certain  sets  of  properties  reoccur   periodically. Discovery -­‐ Meyer  +  Mendeleev -­‐ Mendeleev’s  better  because  left  blank  spaces  for  undiscovered  and  corrected  some  atomic   masses -­‐  No  mention  of  Nobel  Gases  (until  Ramsay) Metals -­‐ Good  conductors,  malleable,  ductile,  high  b/m  points Metalloids -­‐ Look  like  /  behave  like  metals  but  have  non-­‐metallic  properties Nobel  Gases -­‐ Max  number  of  valence  electrons,  dif▯icult  to  alter  this  con▯iguration -­‐ High  degree  of  chemical  inertness Hydrogen -­‐  No  de▯inite  place  on  periodic  table Ion  formation -­‐ Main  group  metals  tend  to  lose  electrons,  with  Al  being  only  non-­‐main  group -­‐ Main  group  non-­‐metals  tend  to  gain  electrons,  as  well  as  N  and  P -­‐ Some  transition  metals  don’t  have  to  achieve  full  shell.  Some  can  achieve  half  (iron) Atomic  Radii -­‐ Probability  of  ▯inding  electron  decreases  with  increasing  distance  from  nucleus,  but  never   0,  so  no  outer  boundaries -­‐ All  that  is  measurable  is  distance  between  nuclei  of  different  adjacent  atoms  (different   depending  on  chemical  bond  or  just  in  contact) -­‐ Covalent  radius,  Metallic  radius,  Ionic  radius -­‐ Ionic  radii  of  cations  smaller  than  neutral.  Ionic  radii  of  anion  larger  than  neutral. -­‐ Isoelectronic  =  same  number  of  electrons   (negative:  larger  radii,  positive:  smaller  radii) Screening  and  Penetration -­‐ Penetration  (how  close  e  gets  to  nucleus) -­‐ Outer  electrons  shielded  by  inner  electrons  as  it  blocks  attractive  nuclear  charge -­‐ Effective  nuclear  charge  =  true  nuclear  charge  -­‐  charge  screened  by  electrons -­‐ Sodium  11  charge,  10  inner  electrons,  therefore  Z =eff   -­‐ Assumptions  incorrect  though  bc  the  amount  of  shielding  varies  as  even  same-­‐ energy  level  electrons  even  occupy  different  spaces  determined  by  probability Trends 1) The  more  electronic  shells  in  an  atom,  the  larger  an  atom  is.  Atomic  radius  increases   from  top  to  bottom  in  a  group. 2) Atomic  radius  decreases  from  left  to  right  in  a  period  (one  additional  charge,  and  since   extra  electron  is  in  outer-­‐shell  shielding  is  not  that  effective) 3) Transition  metals  have  relatively  the  same  atomic  radii Ionization  Energy Quantity  of  energy  a  gaseous  atom  must  absorb  to  expel  an  electron
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