Atomic number means

Find the number of neutrons,electrons,and protons in the following species:
$(i)$ $_{15}^{31}P$
$(ii)$ $_{11}^{23}Na^{+}$
$(iii)$ $_{16}^{32}S^{2-}$
$(iv)$ $_{101}^{235}X$
$(v)$ $_{20}^{40}Ca^{2+}$
$(vi)$ $_9^{19}F^{-}$

Which one of the following is not an iso-electronic pair?

Isotopes are those which contain

The $^{18}O$ isotope of oxygen will have:

Which of the following species are isoelectronic (i.e.,have the same number of electrons)?
$Na^{+}, K^{+}, Mg^{2+}, Ca^{2+}, S^{2-}, Ar$