What is the Lewis structure for HCO2?

Answer 1

"The formate ion (HCO2-) has a carbon atom as the central atom, with a H atom single bonded to the left, an O atom single bonded to the right with two pair of electrons around it, and one double bonded O atom to the top also with two pair of electrons around it. The O atom to the right has an H atom (*) single bonded to it as well."

That would make it H2CO2 which is formic acid, with one protolysable H+ (marked * above) leaving the formate anion HCO2-.

HCO2-has the Molecular Geometry Trigonal Planar (meaning it is written in a flat (=planar) Y-shape and has 120 degree bond angles).

It has the Carbon as the central atom, Oxygen to the right and to the bottom with the Hydrogen to the left. The ion has 18 electrons (remember the ion is negatively charged), which means we will have two single bonds, five lone electron pairs, and one double bond.

One Oxygen atom will have a single bond with three lone electron pairs and containing the negative charge of the ion (this takes 1*2 bonding electrons plus 3x2 lone pair electrons). The other doubel bonded Oxygen will have the double bond (taking 2x2 electrons) with two lone electron pairs (2x2 lone pair electrons).

The central C atom will have also one singel bonded H atom (1x2 singele bonding electrons).

Switching which Oxygen atom contains the double bond will give you its resonance structures.

Answer 2

In ascii :C=O: except the equals sign is 3 lines. The C is triple bonded to the O

Answer 3

:C triple bond O:

.C≡Ȯ: