When we were doing Lewis dot structure of ClO4- why Cl is central atom?
Electronegativity of O is less than Cl so O should be central atom and central atom should be capable of making more than one bond which O can do but still you showed Cl as central atom. Please advise. This is troubling my mind.
It is a simple doubt but troubling me.

Anil
First you are wrong in comparison of electronegativity of oxygen and Chlorine. Oxygen is in 2nd period and is smaller than Chlorine atom.Even on Pauling scale Cl is 3.0 and O is 3.5.Remember three most Electronegative atoms
are N,O and F.Chlorine is considered even less electronegative than N just because it has three shells.
Second you are wrong again that Cl can make only one bond. It can make only one bond if it is not the central atom.However Chlorine can have expanded octet because it is in 3rd period with empty 3d orbitals.Chlorine can make maximum 7 bonds when it is the central atom because it has 7 valence electrons.
In the lewis dot structure of perchlorate ion ,central Cl atom can have max 7 bonds with 4 oxygens. 3 oxygens are doubly bonded and one is singly bonded with formal negative charge.