# What is the formal charge on the Br and O atoms in the BrO_3^- ion?

Nov 19, 2015

$2 \times$ $B r = O$ bonds, and $1$ $\times$ $B r - {O}^{-}$ bond. One $O$ atom bears a negative charge, and the remaining atoms are neutral.
The conventional Lewis structure of bromate ion is ${\left(O =\right)}_{2} B r - {O}^{-}$. Around the doubly bound oxygens there are 6 electrons (hence $O$ is neutral); around bromine there are 7 electrons (4 from the doubly bound oxygens, 1 from the singly bound oxygen and 2 from the lone pair); and around the charged oxygen, there are (necessarily) 7 electrons (one from the $B r - O$ bond and 6 lone pair electrons), so this centre (formally) has a negative charge.