An atom has a mass number of $25$ and contains $13$ neutrons in its nucleus. What is the charge of its ion if it forms a stable octet?

The ratio of the number of neutrons in $_6C^{12}$ and $_{14}Si^{28}$ is ....

List the isotopes of hydrogen,carbon,and chlorine,and specify the number of protons,electrons,and neutrons for each.

The atomic configurations of atoms $A$,$B$,and $C$ are given as: $A = [Z(90) + n(146)]$,$B = [Z(92) + n(146)]$,$C = [Z(90) + n(148)]$. Which of the following statements are incorrect?
$(a) A$ and $C$ are isotones.
$(b) A$ and $C$ are isotopes.
$(c) A$ and $B$ are isobars.
$(d) B$ and $C$ are isobars.
$(e) B$ and $C$ are isotopes.

Give the relation between the following pairs of species:
$(i)$ $_{20}^{40}Ca$ and $_{19}^{40}K$
$(ii)$ $_{17}^{35}Cl$ and $_{17}^{37}Cl$
$(iii)$ $_{18}^{40}Ar$,$_{20}^{40}Ca$ and $_{19}^{40}K$
$(iv)$ $_{38}^{87}Sr$ and $_{38}^{90}Sr$

Isobars are atoms with