Answer:
See explanation
Step-by-step explanation:
The compound P2Br2 contains a pi bond and a sigma bond between two phosphorus atom and then one sigma bond to each of the bromine atoms, hence satisfying the octet of each atom. This compound is covalent in nature since it is composed of two nonmetals.
However, Ba2Br4 involves barium which is a pure metal. Barium mostly forms ionic compounds in which its valency is two. Covalent bonds between two barium atoms is not possible hence the compound Ba2Br4 does not exist.