Here's why:
* Carbon (C) has 4 valence electrons.
* Bromine (Br) has 7 valence electrons, but only needs 1 to complete its octet.
* In CBr4, the carbon atom forms four single bonds with four bromine atoms. This uses up all four of carbon's valence electrons.
* Because all of carbon's valence electrons are involved in bonding, there are no lone pairs left.
Therefore, the central carbon atom in CBr4 has no lone pairs.
