Name CrCl3 and find chromium's state in K2Cr2O7.
Three Cl- make chromium +3: chromium(III) chloride. In K2Cr2O7: K contributes +2, seven O contribute -14, so 2Cr = +12 → each Cr is +6.
Chromium Charge: +2, +3, or +6?
Chromium commonly forms Cr2+ Cr3+ Cr6+ in introductory ionic compounds.
Chromium's workhorse charge is +3 — Cr2O3 is the green of army paint, and Cr3+ colors rubies red. The +6 state appears in bright chromate (CrO4 2-) and dichromate (Cr2O7 2-); the +2 state (blue CrCl2) is unstable in air and mostly a lab curiosity.
| Element | Chromium |
|---|---|
| Symbol | Cr |
| Atomic number | 24 |
| Common ionic charge | +2, +3, +6 |
| Common ions | Cr2+, Cr3+, Cr6+ |
Visual reference
Chromium element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
Where Chromium's charge options come from
Chromium's configuration is unusual: [Ar]3d5 4s1, with a half-filled d shell. Losing three electrons gives the very stable Cr3+ (d3); pushing all six shared electrons toward oxygen gives +6. The half-filled-shell stability is also why chromium metal resists corrosion well enough to be 'chrome.'
This is a classroom reference range, not an exhaustive list of all oxidation states.
The trap in Chromium problems
Treating all chromium compounds as equally safe. Cr3+ is an essential trace nutrient, while Cr6+ (chromates) is toxic and carcinogenic — the villain of the Erin Brockovich case. Same element; the charge state changes the biology entirely.
Worked example: Cr in a formula problem
Cr2+ and Cr3+ and Cr6+ in real compounds
CrCl2
Chromium chloride
Cr2+ balances chloride ions.
CrO
Chromium oxide
Chromium can form oxides where total positive and negative charge balances.
Questions students ask about chromium
What charge is chromium in stainless steel and chrome bumpers?
Zero in the bulk metal — but the surface instantly grows a Cr2O3 film (chromium +3) that seals out oxygen and water. Stainless steel is stainless because of that +3 oxide skin.
Why are rubies red but emeralds green if both get color from Cr3+?
The same Cr3+ ion sits in different host crystals (corundum vs beryl), which squeeze its d orbitals differently. The gap between orbital energies sets which light is absorbed — host changes gap, gap changes color.
How can I tell +6 chromium from +3 in the lab?
Color is the first clue: +6 compounds run yellow (chromate) to orange (dichromate); +3 solutions are green to violet. Adding acid or base flips chromate and dichromate into each other while staying +6.
How do I use this charge in formulas?
Combine positive and negative ions so the total charge is zero — or let the ionic compound calculator do the crossing for you. The full chart lives on the periodic table with charges.
Where this data comes from
Charges and element facts on this page are checked against the primary references below. Found an error? Email hello@periodictablewithcharges.com — corrections ship in the next content update. See how this site is edited.