# What is the geometry of the bicarbonate ion, HCO_3^(-)?

$\text{Bicarbonate anion}$ is trigonal planar with respect to the central carbon atom....
You gots $H O - C \left(= O\right) - {O}^{-}$. There are three regions of electron density round the central carbon, and VESPER insists that these adopt a trigonal planar geometry to minimize the interaction of lone electron pairs. Each $\angle O - C - O = {120}^{\circ}$ to a first approx.