The mass number of $He$ is $4$ and the mass number of $S$ is $32$. How many times is the radius of the $S$ nucleus compared to the radius of the $He$ nucleus?

What is the approximate percentage of the total mass of an atom that is concentrated in its nucleus (in $\%$)?

It is now believed that protons and neutrons (which constitute nuclei of ordinary matter) are themselves built out of more elementary units called quarks. $A$ proton and a neutron consist of three quarks each. Two types of quarks,the so-called 'up' quark (denoted by $u$) of charge $+(2/3)e$,and the 'down' quark (denoted by $d$) of charge $-(1/3)e$ together with electrons build up ordinary matter. Suggest a possible quark composition of a proton and neutron.

$^{22}Ne$ nucleus after absorbing energy decays into two $\alpha$-particles and an unknown nucleus. The unknown nucleus is

Explain the types of atoms by illustrating with examples.

The composition of an $\alpha$-particle can be expressed as: