Question

An example of a compound that contains an atom with an expanded octet of electrons is [1] NaBF4

[2] NH4Cl

[3] SF4

[4] NaClO4

[5] BF3 

Answer 1

Expanded octet means Central atom has more than 8 electrons and in the given compounds NaClO₄ show expanded octet because in this Cl atom has more than 8 electrons IN lewis structure of NaClO₄ we find there are 10 electrons on Cl atom.