An atom of mass number $15$ and atomic number $7$ captures an $\alpha$-particle and then emits a proton. The mass number and atomic number of the resulting product will respectively be

Who discovered the neutron?

${ }_{92}^{238} U$ and ${ }_{90}^{236} Th$ are $\qquad$ of each other.

The three stable isotopes of neon: $_{10}^{20}Ne$,$_{10}^{21}Ne$,and $_{10}^{22}Ne$ have respective abundances of $90.51\%$,$0.27\%$,and $9.22\%$. The atomic masses of the three isotopes are $19.99\;u$,$20.99\;u$,and $21.99\;u$ respectively. Obtain the average atomic mass of neon. (in $;u$)

If the radius of the $^{27}_{13}Al$ nucleus is taken to be $R_{Al}$,then the radius of the $^{125}_{53}Te$ nucleus is nearly

Explain the types of atoms by illustrating with examples.