Answer:
Polyatomic anion
Step-by-step explanation:
Polyatomic anion:
The polyatomic anion is substance having more than one atoms and carrying negative charge.
The poly is Greek word meaning "many". The given compound C₂O²⁻₄
is polyatomic anion because it is made up of more than one atom and have negative charge. The atoms in this compound act as a single unit. In this compound two carbon atoms combine with four oxygen atoms and oxygen carry -2 charge.
In contrast to polyatomic anion, polyatomic cations are also exist. In polyatomic cations positive charge is present in compound and it is also made up of more than one atoms.