Two atoms have the same atomic mass but different atomic numbers. Such atoms are called as:

Two atoms of elements $X$ and $Y$ are isotones of each other. Their mass numbers are $70$ and $72$ respectively. If the atomic number of $X$ is $34$,then the atomic number of $Y$ is ..........

What are nucleons?

The $^{18}O$ isotope of oxygen will have:

Which number is common in isotopes?

$Be^{2+}$ is isoelectronic with: