Which statement is true about a polyatomic ion?

• A. It consists of two or more atoms covalently bonded that act as a single charged unit.
• B. It is always composed of only metal atoms.
• C. It has no net electrical charge.
• D. It cannot participate in ionic compounds.

Answer: (A)

Verified step by step guidance

1. Understand the definition of a polyatomic ion: it is a group of two or more atoms that are covalently bonded together and carry an overall charge.
2. Recall that polyatomic ions can have either a positive or negative charge, meaning they do have a net electrical charge, so the statement 'It has no net electrical charge' is false.
3. Recognize that polyatomic ions are not composed solely of metal atoms; they usually contain nonmetals bonded covalently, so the statement 'It is always composed of only metal atoms' is false.
4. Know that polyatomic ions can participate in ionic compounds by combining with ions of opposite charge to form neutral compounds, so the statement 'It cannot participate in ionic compounds' is false.
5. Conclude that the true statement is: 'It consists of two or more atoms covalently bonded that act as a single charged unit.'