The coordination number of the $\mathrm{B}{\mathrm{a}}^{\mathrm{}2+}$ ions is barium fluoride is 8. The coordination number of the fluoride ion is

${\mathrm{B}\mathrm{a}\mathrm{F}}_2$ is a ­ $\mathrm{A}{\mathrm{X}}_2$ type salt. In its crystal, ${\mathrm{B}\mathrm{a}\mathrm{}}^{2+}$ ions are arranged in ccp arrangement. Since there are two tetrahedral sites for each ${\mathrm{B}\mathrm{a}\mathrm{}}^{2+}$ ion and ${\mathrm{F}}^{-}$ ions occupy all the tetrahedral sites, hence one ${\mathrm{F}}^{-}\mathrm{}$ is surrounded by four ${\mathrm{B}\mathrm{a}\mathrm{}}^{2+}$, i.e., the coordination number of ${\mathrm{F}}^{-}$ is 4.