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

1 Answer
Nov 19, 2015

Answer:

#2xx# #Br=O# bonds, and #1# #xx# #Br-O^-# bond. One #O# atom bears a negative charge, and the remaining atoms are neutral.

Explanation:

The conventional Lewis structure of bromate ion is #(O=)_2Br-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 #Br-O# bond and 6 lone pair electrons), so this centre (formally) has a negative charge.

Note that the number of electrons around the atom of interest determines the formal charge of that atom; single bonds share the electrons between the bound atoms, lone pairs devolve solely to the atom concerned.

Of course in the actual molecule, all of the oxygen atoms are equivalent.