Chromate ion (CrO₄²⁻)
- Charge
- −2
- Atoms
- Cr, O × 4
- Atoms in total
- 5
- Mass of the ion
- 115.992 g/mol
Chromate is one chromium atom bonded to four oxygen atoms, with a 2− charge. Chromium is in the +6 state, and +6 plus four oxygens at −2 each leaves −2. Chromate salts are bright yellow and were once common in paints and anti-rust coatings, but chromium(VI) compounds cause cancer and are now tightly restricted.
- In acid, two chromate ions join and lose an oxygen to form orange dichromate, Cr₂O₇²⁻, so the color shifts from yellow to orange.
- Like sulfate, SO₄²⁻, chromate has a central atom in the +6 state, four oxygens and a 2− charge.
- Lead(II) chromate, PbCrO₄, is the yellow pigment known as chrome yellow.