Question

What are the oxidation numbers in the compound KCl?

Answer 1

The oxidation number of K is +1. The oxidation number of Cl is -1.

You assign oxidation numbers to the elements in a compound by using the Rules for Oxidation Numbers. The important rules for this problem are:

1. The oxidation number of a monatomic ion equals the charge of the ion.

2. The oxidation number of a Group 1 element in a compound is +1.

3. The oxidation number of a Group 17 element in a binary compound is -1.

4. The sum of the oxidation numbers of all the atoms in a neutral compound is 0.

In your case, KCl is an ionic compound. It consists of K⁺ ions and Cl⁻ ions.

The oxidation number of K is +1 (Rules 1 and 2).

The oxidation number of Cl is -1 (Rules 1 and 3).

Note that Rule 4 also applies: +1 + (-1) = 0. KCl is a neutral compound. It has no charge.

Hope this helps.