Correct Answer - Option 2 : Neils Bohr
Explanation:
Bohr's model of Atom:
1. Electrons revolve in different orbits around the nucleus.
- The electron in the hydrogen atom can move around the nucleus in a circular path of fixed radius and energy.
-
These paths are called orbits, stationary states, or allowed energy states.
- These orbits are arranged concentrically around the nucleus.
2. The energy of the electrons in the orbit is quantized.
- The energy of an electron in the orbit does not change with time.
- However, the electron will move from a lower to a higher stationary state when the required amount of energy is absorbed by the electron.
- Energy is emitted when an electron moves from a higher to a lower stationary state.
- The energy change does not take place in a continuous manner.
- Thus, the energy of an electron is quantized.
- The electron in the orbit nearest the nucleus has the lowest energy.
- The energy of an electron is En = - RH(Z2/n2)
where, n=1,2,3...(or) K,L,M,N.. ; Z= 1 for the Hydrogen atom; RH is Rydberg's constant and its value is 2.18 ×10-10J.
E1 = –2.18×10–18 (1/12 ) = – 2.18 × 10–18 J
E2 = –2.18×10–18 (1/22 ) = – 0.545 × 10–18 J
Thus, energies of various levels in the order:
K < L < M < N..... and so on.
Hence, the concept of fixed energy levels around the nucleus was put forward by Neil's Bohr.
Thomson model of Atom:
- The first model of the Atom was proposed by J.J Thomson.
- According to this, the positive charge is spread over a sphere with the electrons embedded in it such that the atom as a whole is electrically neutral.
- This model is also called the Plum pudding model.
Rutherford's Nuclear Model of Atom:
- Ernest Rutherford put forward the Nuclear Model of the Atom.
- This model was proposed on the basis of a Scattering experiment.
- It resembles the solar system.
The postulates of Rutherford's atomic model is as follows:-
1. Most of the mass and all the positive charge of an atom is concentrated in a very small region called a nucleus.
2. The magnitude of the charge on the nucleus is different for atoms of different elements.
3. The nucleus is surrounded by electrons which are revolving around it at very high speeds.
4. Most of the space in an atom is empty.
Bohr's model of Atom:
-
Niel's Bohr proposed Bohr's model of the atom.
- His theory is a modification of Rutherford's model based on the quantum theory of radiation.
The postulates of Bohr's model of Atom is as follows:-
1. The electrons revolve around the nucleus only in certain selected circular paths called Orbits.
2. As long as an electron remains in a particular orbit, it does not lose or gain energy.
3. If an electron jumps from one stationary state to another, it will absorb or emit radiation of a definite frequency.
4. Only those orbits are permitted in which the angular momentum of the electron is a whole no: multiple of \(\frac{h}{{2\pi }}\).
