Question

What is the Lewis Dot Structure for `BrO_2^-` and what are the formal charges on each atom?

Answer 1

We have `7+6+6+1` valence electrons to distribute, i.e. `"10 electron pairs."`

Explanation:

`O=Br-O^-`.

Going from left to right, there are 2 lone pairs on the doubly bound oxygen, 2 lone pairs on Br, and 3 lone pairs on the singly bound oxygen (and since this centre owns 7 electrons, it has a formal negative charge). This distribution of electron pairs about `Br`, bonding and non-bonding, is tetrahedral to a first approx. and the `/_O-Br-O` bond angle should be `104-5""^@`, compressed from the the ideal tetrahedral `/_109.5""^@` by the influence on the non-bonding lone pairs.