Cl as an expanded octet

[Hannah Lee 2F]

How can Cl form an expanded octet? And can someone please provide an example of a compound in which Cl acts as an expanded octet?

[AngieGarcia_4F]

Since Cl is in the third period it can hold electrons in its d shell (3d) and form an expanded octet. I googled it and found the example: ClF3

[MKearney_4G]

I googled it and found the example: ClF3

To add to this, one of the problems on our practice exam was to draw ClO4-, and the only correct way to do it is to know that Cl can access the 3d subshell and accept more electrons. Always check the formal charge to make sure your molecule works out ;)

[Tyler Angtuaco 1G]

Like other elements in Period 3 or higher, atoms can have an expanded octet because a d-subshell is present, although it isn't filled for Period 3. You can think of it as existing, but empty for Period 3 elements. Thus, when Period 3 elements like Cl gain more electrons, their d-orbitals are occupied.