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

Explain isotopes,isobars,isotones,and isomers by giving examples.

Which of the following pairs of nuclei are isobars?

Show that the volume of a nucleus is proportional to its atomic mass number $A$.

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

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.