Briefly explain the elementary particles present in nature.

Find the (i) angular momentum (ii) velocity of the electron revolving in the 5^th orbit of hydrogen atom.
(h = 6.6 x 10^–34 Js, m = 9.1 x 10^–31 kg)

The Bohr atom model is derived with the assumption that the nucleus of the atom is stationary and only electrons revolve around the nucleus. Suppose the nucleus is also in motion, then calculate the energy of this new system.

Calculate the average atomic mass of chlorine if no distinction is made between its different isotopes?

Calculate the density of the nucleus with mass number A.