Name one polyatomic ion which is trivalent.

Explanation

To answer the question, "Name one polyatomic ion which is trivalent," we can follow these steps:

### Step 1: Understand the Definition of a Polyatomic Ion
A polyatomic ion is an ion that consists of two or more atoms that are chemically bonded together, and it carries a charge. This charge can be positive or negative.

### Step 2: Define Trivalent
Trivalent refers to an ion that has a valency of three, meaning it has a charge of either +3 or -3.

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