Oxidation Number of Cl (Chlorine) in Different Compounds

Chlorine shows oxidation states of -1, 0, +1, +3, +5, and +7.

It shows positive oxidation states only when it bonds with atoms that are more electronegative than itself (i.e., Oxygen or Fluorine).

1. Oxidation Number = -1

• Occurs in chlorides (when bonded to metals or less electronegative elements).
• Examples: NaCl, HCl, MgCl₂. (Cl is -1).

2. Oxidation Number = 0

• Occurs in its elemental molecular state.
• Example: Cl₂ gas. (Oxidation state = 0).

3. Oxidation Number = +1

• Example: Hypochlorous acid (HClO).
• Calculation: H(+1) + Cl(x) + O(-2) = 0 → 1 + x - 2 = 0 → x = +1.

4. Oxidation Number = +3

• Example: Chlorous acid (HClO₂).
• Calculation: 1 + x + 2(-2) = 0 → 1 + x - 4 = 0 → x = +3.

5. Oxidation Number = +5

• Example: Chlorate ion (ClO₃⁻) or Chloric acid (HClO₃).
• Calculation for ClO₃⁻: x + 3(-2) = -1 → x - 6 = -1 → x = +5.

6. Oxidation Number = +7 (Maximum possible)

• Example: Perchlorate ion (ClO₄⁻) or Perchloric acid (HClO₄).
• Calculation: 1 + x + 4(-2) = 0 → 1 + x - 8 = 0 → x = +7.