Question

What is the molecular geometry of the `NO_3^–` ion?

Answer 1

Trigonal planar.

Explanation:

There are `3xx6+5+1=24` valence electrons. A Lewis structure of `(O=)N^+(-O)_2^-` is reasonable. Because there are 3 regions of electron density around the central nitrogen, trigonal planar geometry is suggested.

Note that in the given Lewis structure, 3 of the 4 atoms bears a formal charge. The sum of the formal charges: `+1-1-1` is the charge on the ion.