An element consists of a mixture of three isotopes $A$, $B$, and $C$ of masses $m_1$, $m_2$, and $m_3$ respectively. If the relative abundances of the three isotopes $A$, $B$, and $C$ are in the ratio $2:3:5$, the average mass of the element is:

Two nuclei of $Cu^{64}$ are in contact with their surfaces touching. What is the electrostatic potential energy between them in $MeV$?

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

If the mass number of an atom is $A = 40$ and its electron configuration is $1s^2, 2s^2, 2p^6, 3s^2, 3p^6$,the number of neutrons and protons in its nucleus will be

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.

The mass number of an iodine nucleus and a polonium nucleus is $125$ and $216$ respectively. The ratio of the radius of the iodine nucleus to that of the polonium nucleus is: