In the nuclear reaction $X(n, \alpha) _3^7Li$,what is $X$?

In a periodic table,the average atomic mass of magnesium is given as $24.312 \; u$. This average value is based on their relative natural abundance on Earth. The three isotopes and their masses are $_{12}^{24} Mg \; (23.98504 \; u)$,$_{12}^{25} Mg \; (24.98584 \; u)$,and $_{12}^{26} Mg \; (25.98259 \; u)$. The natural abundance of $_{12}^{24} Mg$ is $78.99 \%$. Calculate the abundances of the other two isotopes.

Define nuclear force.

Choose the incorrect statement from the following.

The atomic mass number of an element is $\qquad$ .

Which of the following pairs of nuclei are isobars?