UNIT5:ElectronsinAtoms
CPChemistry
Mrs.Howland
ì
UNITOBJECTIVES
STUDENTSWILLKNOW:
ì 
Theoctetrule
ì 
Theroleofvalenceelectronsinchemicalbonding
ì 
TheelectronconfiguraHonprinciples(AuLau’sPrinciple,PauliExclusionPrinciple,andHund’sRule)
ì 
Thenamesandshapesofelectronorbitals(s,p,d,andf)
ì 
TherelaHonshipbetweenelectromagneHcspectrumandenergy
STUDENTSWILLBEABLETO:
ì 
Describetheoctetruleandtheroleofvalenceelectrons
ì 
WritetheelectronconfiguraHonforvariouselementsintheperiodictableusingtheelectronconfiguraHon
principles
ì 
IdenHfyunknownmetalsinsaltsusingexperimentaldataandknowledgeoftheelectromagneHcspectrum
ATOMS:Whatwealreadyknow
ValenceElectrons
ì  Valenceelectronsareelectronslocatedinthe
outermostshellofanatom
ì  RelaHonshipwithatom’sreacHvity
ì  Theelectronsthatareusedinbonding
DeterminingValenceElectrons
ì  NumberofvalenceelectronsmatchesGROUPNUMBER
(excepthelium!)
YOUTRYIT:
DeterminingValenceElectrons
ì Howmanyvalenceelectronsfor…
ì F
ì C
ì Na
BohrModel
ì  Differentorbitalshaveelectronswithdifferentenergylevels
ì  Modelismostlycorrect,butmissingkeycomponent:
ì  OrbitalsareNOTring-shaped!
‘Actual’OrbitalShape
ì  ‘Actual’orbitalshaperepresentswheretheelectronsare
LIKELYtobelocatedatanygivenHme
ì  Electronorbitalsarestandingwaves
THETRAINISMOVINGAROUNDTHE
TRACK.
AtanygivenBme,whereisthetrain?
ElectronOrbitalShapes
SOURCE:Slideplayer.net
EnergyandOrbitals
ì  TheenergyleveloftheelectronsINCREASESwitheach
sequenHalorbitalshape
OrbitalShapesandSubshells
ì  Thereareacertainnumberofeachorbital(shell)shape
EachOrbitalHoldsLimitedNumberofe-
ElectronConfiguration
ì  HowdowerepresenttheelectronlocaHonsforvarious
elements?
ì  ELECTRONCONFIGURATION
ì  LOOKSLIKE:
OrbitalscorrespondwithPERIODICTABLE
ElectronNOTATION
EXAMPLES:
HOWDOYOUKNOWTHEORDEROFORBITALS???
PRACTICE:
ì  PracHce:
AskthesequesHonseveryHmeyouhavetowriteanelectron
configuraHon
ì 
Lithium:
1. 
2. 
3. 
4. 
5. 
6. 
7. 
findtheelementontheperiodictable
whatistheperiodnumber?
howmanyshells?
whatisthegroupnumber?
howmanyvalenceelectrons?
whatsubshell(s)doesLihave?
whatistheelectronconfiguraHon?
YOUTRYIT:
ì  WhatistheelectronconfiguraHonnotaHonfor:
1)  F
2)Fe
ABBREVIATEDElectronConfigurationNotation
ì 
ForelementsintheTransiHonMetals(groups3-12),shorthand
canbeusedtowriteelectronnotaHon
ì 
UsingclosestNOBLEGAS
ì 
Noblegassesareingroup18!
HOWTODOIT:
1) 
Findsymbolforelementonperiodictable
2) 
Writesymbolinbracketsforclosestnoblegas(locatedtofar
RIGHTinprecedinghorizontalperiod)
3) 
Movebackdowntorowforelement.StarHngatfarLEFT,
completetheelectronconfiguraHonnotaHon
EXAMPLE:AbbreviatedNotation
ZINC
YOUTRYIT!
ì WritetheabbreviatednotaHonfor:
1)  Ti
2)  Pd
ElectronConfiguration–ORBITALDIAGRAM
ì  ORBITALDIAGRAM=ModeltorepresentlocaHon
ofatomswithintheirrespecHveorbitals
ì  THREE(3)RULES:
ì  AuLauPrinciple
ì  PauliExclusionPrinciple
ì  Hund’sRule
AuYauPrinciple
ì  AuQau’sPrinciple:Electronsoccupyorbitalswith
thelowestenergylevelFIRST
PauliExclusionPrinciple
ì  PauliExclusionPrinciple=Eachatomicorbitalmayonly
represent2electronsATMOST
ì  For2electronsinthesameorbital,theymusthaveOPPOSITESPIN
ì  SPIN=quantummechanicalenergyproperty;clockwiseor
counterclockwise
ì  SPINisrepresentedbyVERTICALARROWS:
LEARNINGCHECK!
ì  WhichisCORRECT?
A
B
Hund’sRule
ì  Hund’sRule=Electronsoccupyeachorbitalsothatthespinin
theSAMEDIRECTIONisaslargeaspossible
ì  THENelectronsoccupytheorbitalwithoppositespinpaired
LearningCheck!
ì WhichisCORRECT?