Thomson Atom Model
Thomson Atom Model suggests an atom to be a tiny sphere of radius ≈ 10-10 m, containing the positive charge. The atom is electrically neutral. It contains an equal negative charge in the form of electrons, which are embedded randomly in the sphere, like seeds in a water melon. This model failed to explain
1) Large angle scattering of a particles
2) Origin of spectral lines observed in the spectrum of hydrogen atom.
Rutherford atom model
It was assumed that negatively charged electrons remove around the nucleus in circular or bits. The model failed because it predicted continuous atomic spectrum and an unstable atom which revolving electrons falling into the nucleus due to continuous loss of energy.
Bhor modified Rutherford atom model, by postulating that electrons can revolve around the nucleus in stationary orbits only and energy is radiated only when an electron jumps from an outer stationary orbit (n2) to an inner stationary orbit (n1).
Somerfield atom model
1) Electrons revolve around the nucleus in elliptical orbit.
2) Mass of electron relativistically with its velocity as m = m0/√(1-v2/c)
3) For a particular principal quantum number (n) , there will be sub orbit of different eccentricities of different l values.
4) Total angular momentum of electron is resultant of orbital angular momentum and redial angular momentum. Both are quantized separately.