Write Lewis structures that obey the octet rule for each of the following. Except for HCN and

Question:

Write Lewis structures that obey the octet rule for each of the following. Except for HCN and H2CO, the first atom listed is the central atom. For HCN and H2CO, carbon is the central atom.
a. HCN
b. PH3
c. CHCl3
d. NH4+
e. H2CO
f. SeF2
g. CO2
h. O2
i. HBr