Question

which option contains an example of a polyatomic ion? (1 point)
○ mgcl
○ cacl₂
○ kno₃
○ o₂

Explanation:

1. Recall the definition of a polyatomic ion: a charged species composed of two or more atoms covalently bonded (or with a net charge).
2. Analyze each option:

• \( \text{MgCl} \): Incorrect formula (should be \( \text{MgCl}_2 \) for magnesium chloride), and it contains monatomic ions (\( \text{Mg}^{2+} \), \( \text{Cl}^- \)).
• \( \text{CaCl}_2 \): Contains monatomic ions (\( \text{Ca}^{2+} \), \( \text{Cl}^- \)).
• \( \text{KNO}_3 \): Contains \( \text{K}^+ \) (monatomic) and \( \text{NO}_3^- \) (polyatomic ion, made of N and O atoms with a net charge).
• \( \text{O}_2 \): A diatomic molecule, not an ion.

Answer:

C. \( \text{KNO}_3 \)