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AuroraBorealis– reallifeatomicexcitement
Auroras result from emissions of photons in the upper atmosphere (above 80 km/50 miles), from ionized N 2 atoms regaining an electron, and O 2 and N (^2) atoms returning from an excited state to ground state. Particles accelerated from solar winds transfer energy and excited these species; excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule:
- O (^2) emissionsgreenorbrownishͲred
- N (^2) emissionsblueorred
Topic 3 :AtomicStructure
Learninggoals:
- Understandthenatureoflight
- Understandthebehaviorof electronsandquantizationofenergy
- AtomicLineSpectra
- IntroductiontoQuantumMechanics
- WaveProperties
- QuantumNumbers
- AtomicOrbitals
- Electronicconfigurationsofatoms
Let’s chemistrybuildupmuscles.some
Suggested and6.5,6.15,Problems6.17,6.27,(ataminimum):6.32,6.33,6.43,inͲchapter6.49,6.55,problems 6.57, 6.113,6.63,6.117,6.69,6.121,6.79,6.85,6.87,6.101,6.103,6.105,
Reminder:ProgrammablecalculatorsareNOTallowedforanyquizorexaminC117!!!
You “ex,”will“Ln,”need“Log,”anon“10Ͳprogrammablex,”“1/x”(or“x Ͳ 1 (simple) (^) ”),“x y,”and scientific scientific calculator notation,,withlikefunctiononeofthese:keysfor
iPods,^ No iPhones, orcell phones.
ElectromagneticSpectrum
What’sthecontroversyaboutcellphonefrequencies?
Visiblelightisonlyasmallcomponentofthecontinuumofradiant
energyknownasthe electromagneticspectrum.
c =3.00x 10 8 m/s
c = ʄʆ
TheWaveNatureofLight
Whatisthewavelengthoflight(inmeters)ofanelectromagnetic wavewhosefrequencyis1.61x 1012 sо^1?
ElectromagneticSpectrum
Allcellularphonenetworksworldwideuseaportionoftheradio frequencyspectrumdesignatedasUltraHighFrequency(UHF)for thetransmissionandreceptionoftheirsignals.
Thenew4GiPhoneworksatfrequencies 2500 Ͳ 2690 MHz.
Whatwavelength(ʄ)does2600MHzcorrespondto?
ElectromagneticRadiation
- Muchofourunderstandingoftheelectronic structureofatomscomesfromanalysisofthelight emitted orabsorbed bysubstances.
- Electromagneticradiationoscillateselectricand magneticfieldswhilecarryenergythroughspace.
- Electromagneticradiation =
Matteremitslightintwoprominentways: 1.)BlackbodySpectra
2.)EmissionSpectra
- Patternsinfrequenciesofabsorption/emission
- Continuousspectra
- Linespectra
TypesofSpectra
Whitelight&continuousspectra
Whenradiationfromanylightsourceisseparatedintoits differentwavelengthcomponents,a spectrum isproduced.
Continuousspectrum
Linespectra
- Notallemittedradiationprovidesa continuousspectrumofenergies(colors).
- Whendifferentgasesareplacedunder reducedpressure(vacuum)inatubeanda highvoltage(energy)isapplied,thegases emitdifferentcolorsoflight. - NeappearsredͲorange(15distinct lines) - Helooksalmostwhite.Why? - Happearsavividpurple.Why?
LineSpectra&GasDischargeTubes
Linespectra =
Everyelementhasitsownuniqueemissionspectrum.
In1905, AlbertEinstein usedPlanck’stheory toexplainthe photoelectriceffect. Electronsareejectedfromthesurfaceofa metalexposedtolightofacertain threshold frequency. Thenumberofelectronsejectedis proportionaltotheintensity. Einsteinproposedthatthebeamoflight= streamofparticles= photons****. Eachphoton(oftheincidentlight)must possestheenergygivenbytheequation:
QuantumTheory
Problemsyoushouldbeabletosolve
1. nknown,calculateʄ
2. ʄ known,calculaten
3. photonenergy(E)known,calculatenand/orʄ
4. ʄ ornknown,calculateEforonephoton
5. ʄ ornknown,calculateEforamoleofphotons
Seekhelpatdiscussionandofficehoursifyouareunsure thatyouaredoingtheseproblemscorrectly.
ʄʆ =c E=hʆ E=hc/ʄ h=6.626x 10 Ͳ^34 J•s
Howdoesallthisrelatetodailylife?
Visiblelightdoesn’thurttheskin(evenlotsofit).UVlightdoes. HowdoesdamagerelatetotheenergyoftheUVlight? PABA, pͲaminobenzoic acid, was widely used in sunscreens as a UV filter. It is a UVB absorber, meaning that it can absorb wavelengths between 290Ͳ320 nm. Calculate the amount of energy (in kJ/mol) that it is absorbed assuming 313 nm.
The Rydberg equationcanbeusedtocalculatethewavelengthsofthefour visiblelinesintheemissionspectrumofhydrogen.
- R (^) ь istheRydbergconstant(1.09737317x 10 7 mо^1 )
- ʄ thewavelengthofalineinthespectrum, n (^) 1 and n (^) 2 arepositive integerswhere n (^) 1 > n (^) 2. NeilsBohrattributedtheemissionofradiationbyanenergizedhydrogenatom totheelectrondroppingfromahigherͲenergyorbittoalowerone.
- E (^) n istheenergy
- n isapositiveinteger
- n =ьand E (^) ь = 0
BohrTheory
O^1 = R^ f n^11^2 n^122
§¨ (^) ·¸ © ¹
HeisenbergUncertaintyPrinciple
HeisenbergUncertaintyPrinciple =
x p^ h
' x ' t (^) S 4
x m u^ h
' x ' t S
- ȴ x istheuncertaintyinpositioninmeters;ȴ p istheuncertaintyin
momentum;ȴ u istheuncertaintyinvelocityinm/s; m isthemassin
kg
- Complexmathematicalequations,butcanpredictprobabilityof
electronsatacertainposition– orbitals,notorbits
- Othermethods(involvingapproximations)requiredforsystemswith>
1 electron
Werner (1927)Heisenberg
“IfDeBroglie (1924)wavescanbeparticles,thenwhycan’tparticlesbewaves?”– “In Somebodythatcase,betterboyinventdoIhaveacomputer.”anequation– Schrödingerforyou. (1926)
ErwinNobelSchrödingerPrize 1933
LouisNobeldePrize,Broglie 1929
In the1926,movementErwinSchrödingerofelectronspresentedontheatom.aclassicalequationtoexplain Itincorporatedthewaveandparticlecharacteristicsofelectrons. Wavebehaviorwasdescribedwiththe wavefunction,ʗ. The proportionalprobabilitytoof findingandaniselectroncalled inacertainareaofspaceis.
QuantumMechanics
Wavebehaviorisdescribedwiththe wavefunction , ʗ. Theprobabilityoffindinganelectroninacertainareaof spaceisproportionalto ʗ^2 andiscalled electrondensity. The Schrödingerequation specifiespossibleenergystatesan electroncanoccupyinahydrogenatom. Theenergystatesandwavefunctionsarecharacterizedbya setof. Bohr o
Schrödinger o
QuantumMechanics
Quantumnumbers arerequiredtodescribethe distribution ofelectron density inanatom. Therearethreequantumnumbersnecessarytodescribean .
- Theprincipalquantumnumber( n )–
- Theangularmomentquantumnumber( l )–
- Themagneticquantumnumber( ml )– The electronspinquantumnumber ( m s)isusedtospecifyanelectron’sspin. 4.Therearetwopossibledirectionsofspin –
QuantumNumbers
The electronspinquantumnumber ( m s)isusedto specifyan. Therearetwopossibledirectionsofspin. Allowedvaluesof ms are.
QuantumNumbers
Tosummarizequantumnumbers: principal( n )size angular( l )shape magnetic( ml )orientation
electronspin( ms )directionofspin
Requiredtodescribeanatomicorbital
Requiredtodescribeanelectroninan atomicorbital
2 px
…andthecliffnotesversion…
WhichofthefollowingsetsofQNisnotpossible?
(a)? (b)? (c)?
Quantum number (a) (b) (c) Principal (n) 1 2 3 Angular moment (l) 1 0 2 Magnetic (ml) 0 0 – Electron spin (ms) (^) +½ +½ – ½
QuantumNumbers
All sorbitals aresphericalinshapebutdifferinsize:
1 s < 2 s < 3 s
2 s
AtomicOrbitals
Theenergiesoforbitalsinthehydrogenatomdependonlyontheprincipal quantumnumber.
AtomicOrbitalsEnergies(onHatom)
InamultiͲelectronatoms,the energiesoftheatomicorbitals aresplit.
Howdoesthisrelatetotheperiodictable?
The describeshowtheelectronsare distributedinthevariousatomicorbitals. Ina groundstate hydrogenatom,theelectronisfoundinthe 1 s orbital.
1 s^1
1 s
2 s 2 p 2 p 2 p Energy The m useofanuparrowindicatesandelectronwith s =+½
Groundstateelectron configurationofhydrogen
ElectronicConfigurations
