Which of the following atoms or ions is isoelectronic with neon $(Ne)$?

Which of the following sets of ions represents a group of isoelectronic ions?

$A$ sodium cation $(Na^{+})$ has a different number of electrons from:

In the nucleus of $_{20}Ca^{40}$,there are:

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

Among the following,the isoelectronic species is/are:
$(I)$ $O^{2-}, F^{-}, Na^{+}, Mg^{2+}$
$(II)$ $Na^{+}, Mg^{+}, Al^{3+}, F^{-}$
$(III)$ $N^{3-}, O^{2-}, F^{-}, Ne$