electricity & magnetism lecture 30
TRANSCRIPT
Today’sConcepts:BohrAtomicModel
Electricity & MagnetismLecture 30
Presentation Created by Dr. Adam Lark
Things you asked about:
“ThisactuallykindofmadesenseconsideringIhavedonethisallinchemistry.”
“Isthisreallynecessarytolearnthisinthiscourse??““Couldyoupleaseexplaintherelationshipbetweenthewavelengthsandatomicorbitals??”“Ilikedthisone.”
Question
“Pleaseexplainall4quantumnumbersthattheylistedintheprelecture.”
Rutherford Scattering
+
+
+
+
Ifpositiveandnegativechargesarerandomlydistributedinatoms
Apositivelychargedalphaparticlewillnotbedeflectedbecausethenetchargeisclosetozero.
-
-
-
Ifthepositiveandnegativechargeareseparatedinanatom
Apositivelychargedalphaparticlewillbedeflectedsomeofthetime.
α+
+-α+
-
ElectronsmustorbittheProtons!
-
+
Bridge Question 1
Which of the following scattering patterns correspond to the model of the atom proposed by Rutherford?
Thealphaparticlesmustscatterinall
directions.
Diffraction Grating Spectrometer
Hydrogenlamp
Diffraction Grating spectrometer
VisibleSpectralLinesofHydrogen
BalmerSeries,n=2
m
Aregularpatternoflineswasobserved.
Rydberg Formula
RH=1.097x107m-1
ThewavelengthofthatlightcanbefoundusingtheRydbergformula:
m=initialorbit
n=finalorbit
Rydberg Formula
IntheBohrmodelforthehydrogenatom,whatisthewavelengthofthelightproducedbyanelectronfallingfromthestate,n=3,tothegroundlevel,n=1?.(A)102nm
(B)1367nm
(C)1823nm
(D)102nm
(E)Noneoftheabove
RH=1.097x107m-1
λ apx= 1x 10–7m
Bohr Atomic Model (Hydrogen)
-
-
Electronsinanatomareconfinedtospecificorbits
Whenelectronsjumpfromoneorbittoanother,energyisgainedorlostintheformoflight!
Eachorbithasanenergyassociated
withit:
RydbergEnergy
forn=1:E=E0
E0=2.18x10-18J
forn=1:rn=a0
BohrRadius
Eachorbithasaradiusassociated
withit:
de Broglie orbits
Hypothesis:Wavelengthsofelectronsarerelatedtoenergyandonlyorbitswithintegerwavelengthsareallowed.
E=hf=hc/λλ=hc/E
Bohr Atomic Model
+
RadiusandEnergyScalewithZ,thenumberofprotonsinthenucleus
Energy: Radius:
++
E0=2.18x10-18J
Bridge Question 2
A drawing of the Bohr model of electron orbits in the Hydrogen atom is shown.
Bridge Question 2a
Which of the following will cause an electron transition from n = 1 to n = 2?
A. AphotonwithenergyEphoton=13.6eVB. AphotonwithenergyEphoton=3.4eVC. AnyphotonwithenergyEphoton<10.2eVD. AphotonwithenergyEphoton=11eVE. Noneoftheabove
Bridge Question 2a Explanation
EI=-13.6eV
EF=-3.4eV
Ephoton=10.2eV
AnswerC?
Thephotonmusthaveenergyexactlyequalto10.2eV
AnswerE!
-
Bridge Question 2b
Which of the following transitions will emit a photon with the longest wavelength? Fromn=4ton=3
Fromn=3ton=2
Fromn=2ton=1
Lowerenergy=lowerfrequency
Ephoton=hf
lowerfrequency=longerwavelength
h=4.13×10−15eV⋅s=6.63×10−34 J⋅s
Bridge Question 3
How many possible wavelengths could be observed when a hydrogen atom initially excited to the n = 4 state returns to the ground state?
A. 2 B. 3 C. 4 D. 5 E. 6
n=4 ton=1n=4 ton=2
n=3 ton=1 n=3 ton=2
n=2 ton=1
n=4 ton=3Orbits: 4 3 2 1
Bridge Question 4
AccordingtotheBohrmodel,whichoftheionslistedinthetablebelowwouldhavethesmallestdistancebetweenanelectroninthelowestenergylevelandthenucleus?
A. He
B. Li
C. Be
D. B
LargestZ,smallestr!
Simulation
Hydrogenatomsimulation