# Question #6c7ec

$C a {\left(N {O}_{3}\right)}_{2}$
Calcium nitrate is composed of $C {a}^{2 +}$ and $N {O}_{3}^{-}$ ions. To form an electrically neutral species, clearly I must take 2 nitrate anions per calcium dication.
How do you know that calcium metal forms a $C {a}^{2 +}$ ion? Look at the Periodic Table. Calcium, an alkaline earth, is in Group II (i.e. the vertical column). If it is in Group II it has 2 valence electrons, as does $B e$, and $S r$, and $B a$.