$J. Chadwick$ discovered a subatomic particle which has no charge and has a mass nearly equal to that of a proton. Name the particle and give its location in the atom.

The number of electrons in the outermost '$L$' shell of an atom is $5$.
$(a)$ Write its electronic configuration.
$(b)$ What is its valency and why?

Rutherford's $\alpha-$ particle scattering experiment showed that
$(i)$ Electrons have negative charge
$(ii)$ The mass and positive charge of the atom is concentrated in the nucleus
$(iii)$ Neutron exists in the nucleus
$(iv)$ Most of the space in atom is empty
Which of the above statements are correct?

Who discovered the neutron?

$(a)$ Write two drawbacks of Rutherford's model of an atom.
$(b)$ State Bohr's postulates to overcome the drawbacks of Rutherford's model.

In the atom of an element $X$,$6$ electrons are present in the outermost shell. If it acquires noble gas configuration by accepting the requisite number of electrons,what would be the charge on the ion so formed?