Numford
Oxidation number

Cr in K₂Cr₂O₇

Cr is +6 in potassium dichromate.

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.

Cr+6

  1. K is an alkali metal: +1 in its compounds.
  2. Oxygen is −2 in most compounds.
  3. The oxidation numbers add up to the charge, 0: 2(+1) + 7(−2) + 2x = 0.
  4. 2x = +12, so x = +6.
Rule steps

How to find it

  1. K is an alkali metal: +1 in its compounds.
  2. Oxygen is −2 in most compounds.
  3. The oxidation numbers add up to the charge, 0: 2(+1) + 7(−2) + 2x = 0.
  4. 2x = +12, so x = +6.
Every atom

All the oxidation numbers in K₂Cr₂O₇

  • K +12 atoms, alkali metal
  • O −27 atoms, oxygen
  • Cr +62 atoms, sum rule
Questions

Cr in K₂Cr₂O₇: quick answers

What is the oxidation number of Cr in K₂Cr₂O₇?

Cr in K₂Cr₂O₇ (potassium dichromate) is +6.

How do you find the oxidation number of Cr in K₂Cr₂O₇?

K is an alkali metal: +1 in its compounds. Oxygen is −2 in most compounds. The oxidation numbers add up to the charge, 0: 2(+1) + 7(−2) + 2x = 0. 2x = +12, so x = +6.

What are the oxidation numbers of the other atoms in K₂Cr₂O₇?

K +1, O −2. Together with Cr at +6 they add up to the charge of the compound, 0.

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