Which of the following species does not have the same number of electrons as the other three species?

$A$ sodium cation $(Na^+)$ has a different number of electrons from which of the following species?

The number of protons,neutrons,and electrons in the element $_{89}^{231}Y$ is:

Which one of the following is not isoelectronic with ${O^{2-}}$?

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

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 $_{38}^{90}Sr$