From the following pairs of ions,which one is not an iso-electronic pair?

Match the following columns:

$(i) \ _{26}Fe^{54}, \ _{26}Fe^{56}, \ _{26}Fe^{58}$	$(a) \ \text{Isotopes}$
$(ii) \ _1H^3, \ _2He^3$	$(b) \ \text{Isotones}$
$(iii) \ _{32}Ge^{76}, \ _{33}As^{77}$	$(c) \ \text{Isoelectronic}$
$(iv) \ _{92}U^{235}, \ _{90}Th^{231}$	$(d) \ \text{Isobars}$
$(v) \ _1H^1, \ _1D^2, \ _1T^3$

Which of the following species are isoelectronic: $Na, Na^+, F^-, F$?

What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.
$(i)$ $F^{-}$
$(ii)$ $Ar$
$(iii)$ $Mg^{2+}$
$(iv)$ $Rb^{+}$

The nitride ion in lithium nitride is composed of:

An ion with mass number $56$ contains $3$ units of positive charge and $30.4 \%$ more neutrons than electrons. Assign the symbol to this ion.