Step 1: Count the total number of valence electrons. The C atom (IVA) has four and the O atom (VIA) has six, giving `(4+6=)10` valence electrons.
Step 2: Draw the skeleton structure. Since carbon monoxide molecule is diatomic, its skeleton structure is simply written as
`C-O`
Step 3: The number of valence electrons used to form single bond between C and O is 2, leaving `(10-2=)8` electrons to complete the octets of C and O atoms.
Step 4: The number of valence electrons required to complete all octets is [6 (for C atom) + 6 (for O atom)=] 12.
Step 5: Since the number of valence electrons left (8) is four less than the number of electrons needed to complete all octets, two additional covalent bond must be drawn in the Lewis structure to give
`C-=O`
The Lewis structure is finished by placing the suitable number of dots to complete the octet around each atom:
`:C-=O:`
Step 6: Two lone pairs `(4e^(-)s)` and three bonding pairs `(6e^(-)s)` give a total of `10e^(-)s` which is equal to the number of valence electrons counted in step 1. The octet of every atom is satisfied.
