The polyatomic name for CH3COO- is acetate. This formula is more accurate because it represents the actual structure of the ion. The -COO- group is called a carboxylate group, and it consists of a carbon atom bonded to two oxygen atoms. The carbon atom is also bonded to a hydrogen atom, which gives the acetate ion its overall formula of CH3COO-.

The formula CH3COO- is more accurate than the formula C2H3O2- because it shows the actual connectivity of the atoms in the ion. The formula C2H3O2- suggests that the ion consists of two carbon atoms, three hydrogen atoms, and two oxygen atoms, but it does not show how these atoms are bonded together. The formula CH3COO- shows that the ion consists of a carbon atom bonded to three other atoms: two oxygen atoms and a hydrogen atom.