$_{20}X^{40}$ and $_{21}X^{40}$ 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.

Among the following,the set of isoelectronic ions is:

Positive ions are formed from the neutral atom by the

Which of the following species is $NOT$ isoelectronic with neon?

Which of the following pairs represents isobars?