State any two Bohr ' s postulates and write the energy value of the ground state of the hydrogen atom.

Two of Bohr's postulates are: 1. The electrons revolve only on that orbit whose angular momentum is an integral multiple of h 2 π . L = m v r = n h 2 π 2. When an electron jumps from a higher energy level to a lower energy level, they radiate energy in the form of h ϑ . E 2 - E 1 = h ϑ where , h = Planck ' s constant ϑ = frequency of the radiation The energy value of the ground state of the hydrogen atom is - 13 . 6 eV .

What conclusion is drawn from Rutherford ' s scattering experiment of α ‐ particles?

The conditions are drawn from Rutherford's scattering experiments of α - particles are: 1. An atom consists of an extremely small central core, called the nucleus, in which almost the entire mass and the whole of the positive charge of the atom is concentrated. 2. The part of the atom surrounding the nucleus is hollow.

Name the series in the atomic spectra of the hydrogen atom that falls in the ultra violet region.

Ultraviolet region covers the wavelength range of 100 ‐ 400 nm . Lyman series in the atomic spectra of the hydrogen atom falls in the ultra violet region. For a given principal quantum number n , the electronic transitions takes place from n ≥ 2 to n = 1 . Balmer series lies in visible region, Paschen series lies in near infrared region whereas Bracket, Pfund as well as Humphrey series lie in far infrared region of electromagnetic spectrum.

Calculate the minimum wavelength of the spectral line present in Balmer series of hydrogen.

For the minimum wavelength line of the Balmer series the transition will take place between n 1 = 2 and n 2 = ∞ The wave number ν of the associated wave will be: ν = R H [ 1 n 2 1 − 1 n 2 2 ] Where, Rydberg Constant, R H = 109677 cm - 1 Substitute the values in the equation, = 109677 [ 1 2 2 − 1 ∞ 2 ] cm − 1 = 109677 × 1 4 cm − 1 ∵ λ = 1 ν = 3 . 647 × 10 − 5 cm = 3647 A o ,