Example 1:   ClO₂^-

ClO₂^-    Total number of electrons 7 + 2 x 6 + 1 = 20 = 10 pairs

Identify the central atom and connect the peripheral atoms with a pair of electrons as two dots and count the remaining electron pairs

20-4 = 16 electrons left (8 pairs)

Complete the octet of oxygen atoms and count the remaining electron pairs

16-12 = 4 electrons

Complete the octet of chlorine atom,

Since all the electrons are utilized and octet is satisfied, no need of any multiple bonds.

The structure is or or

Example 2: CO

CO (carbond monoxide) Total number of electrons 4 + 6 = 10

Connect the two atoms with a pair of electrons as two dots and count the remaining electron pairs

10-2 = 8 electrons left

Complete the octet of oxygen atoms and count the remaining electron pairs

8-6 = 2 electrons

Place the remaining electron pair on carbon atom,

All the electrons are utilized and octet is not satisfied for carbon as there is a shortage of four more electrons.

Drag two electron pairs on oxygen atom in between carbon and oxygen to establish two more bonds so that a triple bond exists between C and O which satisfies the octet of both C and O.

The structure is or or