Which polyatomic ion is found in the compound represented by the formula nahco3?
(1) acetate (3) hydrogen sulfate
(2) hydrogen carbonate (4) oxalate

Answer is (2) - hydrogen carbonate

Explanation:

NaHCO₃ is an ionic compound which is made from Na⁺ and HCO₃⁻ ions. The decomposition is

NaHCO₃ → Na⁺ + HCO₃⁻

Among the resulted ions, Na⁺ is a monatomic ion while HCO₃⁻ is a polyatomic ion.

Polyatomic ions mean ions which are made of two or more different atoms.

HCO₃⁻ is made from 3 atoms as H, C and O. The name of HCO₃⁻ ion is bicarbonate or hydrogen carbonate.