Question

The elliptical orbits of electron in the atom were proposed by
(A) J.J. Thomson
(B) Bohr
(C) Sommerfeld
(D) De Broglie

Answer 1

Hint: We should know that electrons are the subatomic particles that orbit the nucleus of an atom. They are generally negative in charge and are much smaller than the nucleus of the atom. Electrons are the negatively charged particles of an atom. Together, all of the electrons of an atom create a negative charge that balances the positive charge of the protons in the atomic nucleus. Electrons are extremely small compared to all of the other parts of the atom. Electrons have the smallest electrical charge. This electrical charge equals the charge of a proton, but has the opposite sign. For this reason, electrons are attracted by the protons of atomic nuclei and usually form atoms. An electron has a mass of about 1/1836 times a proton.

Complete step by step answer
We know that in an atom, electrons (negatively charged) revolve around the positively charged nucleus in a definite circular path called orbits or shells. Each orbit or shell has a fixed energy and these circular orbits are known as orbital shells.
It is known that Bohr's gave the concepts of orbits and did careful experiments to reveal extra spectral lines but he didn't find desired results. Then Somerfield proposed elliptical electron orbits to explain these effects which gave the desired results. Electrons orbit the nucleus in orbits that have a set size and energy. The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit. Radiation is absorbed or emitted when an electron moves from one orbit to another.
Now the two weaknesses of Bohr's atomic model are:
1) The path of the electron around the nucleus is considered to be circular of definite radius but in reality, it can be at any distance from the nucleus.
2) The model is based on spectra of atoms and newton's laws of motion which are not applicable to microscopic particles.

Hence the correct option is option C.

Note: We say that the Bohr model failed because it failed to take into account one thing: synchrotron radiation. The Bohr model says that electrons whizz around the atomic nucleus in the same way that the earth goes around the sun - but rather than being bound by gravity, it is bound by electromagnetic forces. The Bohr model showed us a great deal more information on the atom and describes it in better detail for us to understand more clearly. The Bohr Model explains to us that electrons or negative charges orbit around the atom's nucleus in energy levels. It also describes that electrons can change energy levels.