For a nucleus to be stable,the correct relation between neutron number $N$ and proton number $Z$ is

Four statements are given ($A$ is mass number) :
$A$. The volume of a nucleus is proportional to $A^{1/3}$.
$B$. The volume of a nucleus is proportional to $A$.
$C$. The difference in mass of an atom and its nucleus is called the mass defect.
$D$. The difference in mass of a nucleus and its constituents is called the mass defect.
Choose the correct answer from the options given below :

The particles which can be added to the nucleus of an atom without changing its chemical properties are called:

An unstable heavy nucleus at rest breaks into two nuclei which move away with velocities in the ratio of $8:27$. The ratio of the radii of the nuclei (assumed to be spherical) is

Ratio of specific charge of $\alpha$-particle to that of proton is

The nearest distance between two atoms in case of a $bcc$ lattice is equal to