Numford
Oxidation number

S in SO₃²⁻

S is +4 in the sulphite ion.

Oxidation number

Type a formula or an ion: K2Cr2O7, Cr2O7 2-, MnO4-, NH4+ or K4[Fe(CN)6]. Put a known ion in brackets when two elements are unknown. Pick an element to solve for it.

S+4

  1. Oxygen is −2 in most compounds.
  2. The oxidation numbers add up to the charge, −2: 3(−2) + x = −2.
  3. x = +4.
Rule steps

How to find it

  1. Oxygen is −2 in most compounds.
  2. The oxidation numbers add up to the charge, −2: 3(−2) + x = −2.
  3. x = +4.
Every atom

All the oxidation numbers in SO₃²⁻

  • O −23 atoms, oxygen
  • S +41 atom, sum rule
Questions

S in SO₃²⁻: quick answers

What is the oxidation number of S in SO₃²⁻?

S in SO₃²⁻ (the sulphite ion) is +4.

How do you find the oxidation number of S in SO₃²⁻?

Oxygen is −2 in most compounds. The oxidation numbers add up to the charge, −2: 3(−2) + x = −2. x = +4.

What are the oxidation numbers of the other atoms in SO₃²⁻?

O −2. Together with S at +4 they add up to the charge of the ion, −2.

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