Question

draw the lewis structure for formic acid (ch₂o₂). formic acid molecules have one hydroxy group and one carbonyl group. be certain you include any lone pairs.

Explanation:

Step1: Determine valence electrons

Carbon has 4 valence - electrons, hydrogen has 1 valence - electron, and oxygen has 6 valence - electrons. For $CH_2O_2$, the total number of valence electrons is $4+(2\times1)+(2\times6)=18$.

Step2: Place the central atom

Carbon is the central atom as it is the least electronegative among $C$, $H$, and $O$.

Step3: Connect atoms with single bonds

Connect the carbon atom to two hydrogen atoms with single bonds ($C - H$) and to one oxygen atom with a single bond ($C - O$) and to another oxygen atom with a single bond ($C - O$). This uses 4 pairs of electrons.

Step4: Fill octets

The oxygen in the $C - O$ bond (hydroxy - group) needs 3 lone pairs to complete its octet. The other oxygen (carbonyl - group) forms a double bond with carbon ($C = O$) and has 2 lone pairs to complete its octet. The carbon atom has a full octet with 4 bonds. The hydrogen atoms have their duets satisfied with the single $C - H$ bonds.

Answer:

The Lewis structure has a carbon atom in the center. It is bonded to two hydrogen atoms with single bonds, to an oxygen atom (in the $-OH$ group) with a single bond and this oxygen has 3 lone pairs, and to another oxygen atom (carbonyl oxygen) with a double bond and this oxygen has 2 lone pairs.