Two nucleons are at a separation of $1 \times 10^{-15} \ m$. The net force between them is $F_1$ if both are neutrons,$F_2$ if both are protons,and $F_3$ if one is a proton and the other is a neutron. In such a case:

Which of the following is true for a sample of isotopes containing $^{235}U$ and $^{238}U$?

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:

Define the different terms used for the composition of a nucleus.

Consider the following statements ($X$ and $Y$ stand for two different elements):
$(I)$ ${ }_{32}^{65} X$ and ${ }_{33}^{65} Y$ are isotopes.
$(II)$ ${ }_{42}^{86} X$ and ${ }_{42}^{85} Y$ are isotopes.
$(III)$ ${ }_{85}^{174} X$ and ${ }_{88}^{177} Y$ have the same number of neutrons.
$(IV)$ ${ }_{92}^{235} X$ and ${ }_{94}^{235} Y$ are isobars.
Which of the above statements are correct?

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