Dot and cross diagram of thé bond in CLO4-

Step 1: Calculate the total number of valence electrons.
Chlorine (Cl) is in Group 17, so it has 7 valence electrons.
Oxygen (O) is in Group 16, so it has 6 valence electrons.
The ion has a -1 charge, so add 1 electron.
Total valence electrons = $7 + (4 \times 6) + 1 = 7 + 24 + 1 = 32$ electrons.

Step 2: Determine the central atom and draw the skeletal structure.
Chlorine is less electronegative than oxygen, so it is the central atom.

$$\text{O} - \text{Cl} - \text{O}$$ $$\quad |$$ $$$$