Which is a polyatomic ion? Mg2+ O2– NH4+ Na+

1 answer

A polyatomic ion is an ion composed of two or more atoms that are covalently bonded together and carries a net charge. Among the options you provided:

  • Mg²⁺ is a monatomic ion (magnesium ion).
  • O²⁻ is also a monatomic ion (oxide ion).
  • NH₄⁺ is a polyatomic ion (ammonium ion).
  • Na⁺ is a monatomic ion (sodium ion).

Thus, the polyatomic ion from your list is NH₄⁺.