In the Lewis structure of the ion $B_r{F}_2{-}^1$, how many lone pairs are on the central bromine atom?

Draw single bonds between the central bromine atom and each fluorine atom. Each bond uses 2 electrons, so 2 bonds use 4 electrons. Subtract these from the total valence electrons: 22 - 4 = 18 electrons remaining.

Distribute the remaining electrons as lone pairs to satisfy the octet rule for the fluorine atoms first. Each fluorine needs 6 more electrons (3 lone pairs) to complete its octet, so 2 fluorines × 6 electrons = 12 electrons used. Subtract these from the remaining electrons: 18 - 12 = 6 electrons left.