$({}_{32}Ge^{76}, {}_{34}Se^{76})$ and $({}_{14}Si^{30}, {}_{16}S^{32})$ are examples of

An element with mass number $81$ contains $31.7\%$ more neutrons as compared to protons. Assign the atomic symbol.

When a sulphur atom becomes a sulphide ion,

The number of protons,neutrons and electrons in ${}^{13}_{6}C$ respectively are

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.

Which of the following does not contain a number of neutrons equal to that of $_{18}^{40}Ar$?