History of Atomic Models1912:Rutherfordproposedthe“PlanetaryModel "of the atomi.e., positively charged coresurrounded by electrons(1908Nobelprizechemistryofradioactivesubstances)Rutherford estimated the diameter of nucleus to be only about 10-15m. The diameter of an atom, however, was known to be 10-10 m,about 100 000 times larger. Thus most of an atom is empty space.12
History of Atomic Models 1912: Rutherford proposed the “Planetary Model ” of the atom, i.e., positively charged core surrounded by electrons. Rutherford estimated the diameter of nucleus to be only about 10-15 m. The diameter of an atom, however, was known to be 10-10 m, about 100 000 times larger. Thus most of an atom is empty space. (1908 Nobel prize chemistry of radioactive substances)
The planetary model failed in explaining why collapses ofelectronsintonucleusdonotoccur!1)AccordingtoMaxwelltheoryof-eelectronelectromagnetism,astheelectronorbits aroundthenucleus,itacceleratesandhenceradiates-eprotonenergy.2)Thetypicaltimefortheelectrontocollapsesintothenucleuswouldbeabout 10-8s3)Thespectrumofradiationwouldbecontinuous12
1) According to Maxwell theory of electromagnetism, as the electron orbits around the nucleus, it accelerates and hence radiates energy. 2) The typical time for the electron to collapses into the nucleus would be about 10-8 s. 3) The spectrum of radiation would be continuous. +e proton -e electron The planetary model failed in explaining why collapses of electrons into nucleus do not occur!
1913:NielsBohr proposed hisBohrmodel ofthe atom withincorporation of the idea of“quanta"(by Plank & Einstein)TheBohrModelExplanationoftheThreeSeriesofSpectralLinesn=6=0月三56n=5n=4Infrarede)n=3Visiblen=2Visible-100seriesInfraredseriesUltraviolet series-200Ultraviolet-218circular orbits with fixed energyB100200andangularmomentumWavelength (nm)
1913: Niels Bohr proposed his Bohr model of the atom with incorporation of the idea of “quanta” (by Plank & Einstein). circular orbits with fixed energy and angular momentum
BohratomFMerits:+Zei)Explains why atoms are stableii) Predicts energy is quantizediii)ExplainsHatomspectraDemerits:iv)Fails to predict fine spectral structure ofH)Fails for many-electron atomseisclassicalparticlee in orbit'at fixed r corresponding to a quantumnumber.12
Bohr atom Merits: i) Explains why atoms are stable ii) Predicts energy is quantized iii) Explains H atom spectra Demerits: iv) Fails to predict fine spectral structure of H v) Fails for many-electron atoms e - is classical particle e - in ‘orbit’ at fixed r corresponding to a quantum number. v F -e r +Ze
Bohr atome-is a classicalparticlee- in ‘orbit' at fixed r1（1926）Schrodinger atom1)Electronconfinedinan atomshould also behave like a wave.Schrodinger equation!2)Nofixed orbits but electrondensity distribution3)For3-D,weneedthree12quantum numbers n, l, m
Schrödinger atom (1926) 1) Electron confined in an atom should also behave like a wave. 2) No fixed orbits but electron density distribution 3) For 3-D, we need three quantum numbers n, l, ml Bohr atom e - is a classical particle e - in ‘orbit’ at fixed r Schrödinger equation！