Which of the following is the correct chemical formula for the polyatomic ion ammonium?

• A. NH_4^-
• B. NO_3^-
• C. NH_4^+
• D. NH_3^+

Answer: (C)

Verified step by step guidance

1. Understand that a polyatomic ion is a charged species composed of two or more atoms covalently bonded together that carry an overall charge.
2. Recall that the ammonium ion is a common polyatomic ion formed by nitrogen and hydrogen atoms with a positive charge.
3. Analyze the given options and their charges: \(\mathrm{NH_4^-}\) (negative charge), \(\mathrm{NO_3^-}\) (nitrate ion, negative charge), \(\mathrm{NH_4^+}\) (ammonium ion, positive charge), and \(\mathrm{NH_3^+}\) (not a common stable ion).
4. Recognize that the ammonium ion has the formula \(\mathrm{NH_4^+}\), which consists of one nitrogen atom bonded to four hydrogen atoms and carries a +1 charge.
5. Conclude that the correct chemical formula for the ammonium ion is \(\mathrm{NH_4^+}\).