State the postulates of Bohr’s atomic model:
Bohr modified Rutherford’s model by applying Quantum theory to elucidate the structure of hydrogen atoms. The Postulates of Bohr are:
1. An atom consists of a dense nucleus situated at the center with the electron revolving around it. An electron can’t rotate about the nucleus in any chosen orbit but in certain selected orbits only whose angular momentum (mvr) is an integral multiple of h/2π, i.e, mvr = nh/2π
where m= mass of the electron, v= velocity of the electron, n= 1, 2, 3,…=number of orbits in which the electron is present and it is known as the principal quantum number, r = radius of the orbit, and h = Plank’s constant.
When an electron rotates along any of the selected orbits, it doesn’t radiate energy at all. These quantum-selected orbits are called stationary orbits, not that the electron is stationary but that no radiation occurs during the rotation of electrons along these orbits.
2. If energy is supplied to an electron, it may jump from a lower energy level to a higher energy level by absorbing energy. Similarly, the excited electron jumps down to a lower energy level by emitting energy.
Thus, energy absorbed or emitted if an electron jumps can be represented by the following equation:
Δ = E2 ~ E1 = hv.
Where E1 and E2 are the energies of the electron in the first and second energy levels and v is the frequency of radiation absorbed or emitted.