The range of weak nuclear force is of the order of

Consider the following statements:
$I$. All isotopes of an element have the same number of neutrons.
$II$. Only one isotope of an element can be stable and non-radioactive.
$III$. All elements have isotopes.
$IV$. All isotopes of carbon can form chemical compounds with oxygen-$16$.
Choose the correct option regarding an isotope.

The coordination number of $Cu$ is

$A$ heavy nucleus at rest breaks into two fragments which fly off with velocities in the ratio $3: 1$. The ratio of radii of the fragments is

Let the binding energy per nucleon of a nucleus be denoted by $E_{bn}$ and the radius of the nucleus be denoted by $r$. If the mass numbers of nuclei $A$ and $B$ are $64$ and $125$ respectively, then:

For a nucleus of mass number $A$ and radius $R$,the mass density of the nucleus can be represented as: