How many molecules or ions are linear in shape?

$\begin{array}{l}{\mathrm{BeCl}}_2\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{XeF}}_2\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{CIF}}_2^{-}\\ {\mathrm{I}}_3^{-}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{I}}_3^{+}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{\mathrm{BF}}_2^{+}\\ {\mathrm{SnCl}}_2\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\end{array}$

${\mathrm{BeCl}}_2,{ \mathrm{XeF}}_2, {\mathrm{ClF}}_2^{-}, {\mathrm{I}}_3^{-},{ \mathrm{BF}}_2^{+}$are molecules or ions are linear in shape

${\mathrm{SnCl}}_2$ has one lone pair, two sigma bonds, $s{p}^2$ hybridization, and a bent molecular structure. A non-linear molecule as a result.

Molecular geometry for ${\mathrm{I}}_3^{-}$is linear. There are three iodine atoms, because one of them has a negative charge, there are also three lone pairs of electrons and two bond pairs. It will have a 5-steric number. The three lone couples will push back against one another and adopt equatorial orientations.