Thé bond between CLO4-

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.

Chlorine is less electronegative than oxygen, so it is the central atom.
The most stable Lewis structure for $\text{ClO}_4^-$ has chlorine forming three double bonds with oxygen atoms and one single bond with