Numford
Oxidation number

P in H₃PO₄

P is +5 in phosphoric acid.

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.

P+5

  1. Hydrogen is +1 when bonded to non-metals.
  2. Oxygen is −2 in most compounds.
  3. The oxidation numbers add up to the charge, 0: 3(+1) + 4(−2) + x = 0.
  4. x = +5.
Rule steps

How to find it

  1. Hydrogen is +1 when bonded to non-metals.
  2. Oxygen is −2 in most compounds.
  3. The oxidation numbers add up to the charge, 0: 3(+1) + 4(−2) + x = 0.
  4. x = +5.
Every atom

All the oxidation numbers in H₃PO₄

  • H +13 atoms, hydrogen
  • O −24 atoms, oxygen
  • P +51 atom, sum rule
Questions

P in H₃PO₄: quick answers

What is the oxidation number of P in H₃PO₄?

P in H₃PO₄ (phosphoric acid) is +5.

How do you find the oxidation number of P in H₃PO₄?

Hydrogen is +1 when bonded to non-metals. Oxygen is −2 in most compounds. The oxidation numbers add up to the charge, 0: 3(+1) + 4(−2) + x = 0. x = +5.

What are the oxidation numbers of the other atoms in H₃PO₄?

H +1, O −2. Together with P at +5 they add up to the charge of the compound, 0.

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