What is the electrovalency of an ion? Give an example.

(N/A) The electrovalency of an ion is defined as the number of unit charges present on the ion.
Example: In $NaCl$,the $Na^{+}$ ion has one unit of positive charge,so its electrovalency is $+1$. In $CaF_{2}$,the $Ca^{2+}$ ion has two units of positive charge,so its electrovalency is $+2$.
Similarly,in $F^{-}$ and $Cl^{-}$,there is one unit of negative charge,so the valency is $-1$.

Valency	Examples
$+1$	$Na^{+}, K^{+}, Rb^{+}, Cs^{+}, H^{+}, Cu^{+}, Hg^{+}, NH_{4}^{+}$
$+2$	$Mg^{2+}, Ca^{2+}, Sr^{2+}, Ba^{2+}, Cu^{2+}, Cd^{2+}, Ti^{2+}, Cr^{2+}, Mn^{2+}, Fe^{2+}$
$+3$	$Al^{3+}, Sc^{3+}, Cr^{3+}, Fe^{3+}$
$+4$	$Si^{4+}, Sn^{4+}$
$-1$	Halogen (e.g.,$F^{-}, Cl^{-}, Br^{-}, I^{-}$),$H^{-}, OH^{-}, NO_{3}^{-}$
$-2$	Oxygen group $(O^{2-}, S^{2-}, Se^{2-}, Te^{2-})$,$CO_{3}^{2-}, SO_{4}^{2-}$
$-3$	Nitrogen group $(N^{3-}, P^{3-})$,$PO_{4}^{3-}, AsO_{4}^{3-}$