Which of the following elements is isoelectronic with $Na^{+}$?

An isotone of $_{32}Ge^{76}$ is:
$(i) \, _{32}Ge^{77}$
$(ii) \, _{33}As^{77}$
$(iii) \, _{34}Se^{77}$
$(iv) \, _{34}Se^{78}$

The number of protons,electrons and neutrons in a species are equal to $17$,$18$ and $18$ respectively. Which of the following will be the proper symbol of this species?

Find the correct set with isoelectronic species.

The number of protons,neutrons and electrons in the ion ${ }_{16}^{32} S^{2-}$ respectively are

$_{18}Ar^{40}$,$_{20}Ca^{40}$ and $_{19}K^{40}$ are