Write the formula for rhodium(III) oxide.
Rh3+ and O2- cross to Rh2O3 — the same pattern as aluminum and iron(III) oxides. It forms as a protective gray film if rhodium is heated in air.
What Is the Charge of Rhodium?
Rhodium commonly forms Rh3+ in introductory ionic compounds.
Rhodium chemistry is overwhelmingly Rh3+ — Rh2O3, RhCl3 — making it one of the simpler platinum-group metals to learn. Most working rhodium, though, sits at charge 0 inside your car's catalytic converter, scrubbing NOx from exhaust.
| Element | Rhodium |
|---|---|
| Symbol | Rh |
| Atomic number | 45 |
| Common ionic charge | +3 |
| Common ions | Rh3+ |
Visual reference
Rhodium element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
Where Rhodium's charge options come from
Rhodium is [Kr]4d8 5s1. The +3 state (d6) is exceptionally comfortable — low-spin d6 complexes are the poster children of stability in coordination chemistry — so rhodium rarely strays from it in simple compounds. The +1 state matters in industrial catalysis cycles.
This is a classroom reference range, not an exhaustive list of all oxidation states.
The trap in Rhodium problems
Assuming the most expensive metal must have exotic charge behavior. Rhodium's record prices (it has traded above gold many times over) come from scarcity and catalytic demand, not chemistry: its charge rules are among the most predictable in the d-block.
Worked example: Rh in a formula problem
Rh3+ in real compounds
RhCl3
Rhodium chloride
Rh3+ balances chloride ions.
Rh2O3
Rhodium oxide
Rhodium can form oxides where total positive and negative charge balances.
Questions students ask about rhodium
What charge is the rhodium plating on white gold?
Zero — jewelers electroplate a micron of neutral rhodium metal for its brilliant, tarnish-proof white. During the plating itself, Rh3+ ions in the bath gain three electrons each to become that metal film.
Why does the catalytic converter need rhodium specifically?
Neutral rhodium surfaces are uniquely good at tearing apart NO molecules, letting nitrogen pair off harmlessly as N2. Platinum and palladium handle the CO and hydrocarbons; NOx is rhodium's job.
What is rhodium(I) used for if +3 is standard?
Industrial homogeneous catalysis: Wilkinson's catalyst and the Monsanto acetic-acid process both cycle rhodium between +1 and +3. Each round trip through those charges stitches molecules together at ton scale.
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.