Write the formula for cadmium sulfide and name its famous use.
Cd2+ with S2- pairs one-to-one: CdS. As 'cadmium yellow' it colored works by Monet and Van Gogh; today it also serves as a semiconductor in light sensors.
What Is the Charge of Cadmium?
Cadmium commonly forms Cd2+ in introductory ionic compounds.
Cadmium is 2+ everywhere: CdS (the brilliant 'cadmium yellow' of oil paints), CdCl2, and the CdTe of thin-film solar panels. Like zinc directly above it, it has one charge and no exceptions — and unlike zinc, it is seriously toxic.
| Element | Cadmium |
|---|---|
| Symbol | Cd |
| Atomic number | 48 |
| Common ionic charge | +2 |
| Common ions | Cd2+ |
Visual reference
Cadmium element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
Where Cadmium's charge options come from
Cadmium is [Kr]4d10 5s2 — zinc's configuration one row down. The 5s pair leaves; the full 4d10 shell stays shut. Its toxicity flows from that same resemblance: Cd2+ slips into the zinc-shaped sites of enzymes and the calcium-shaped sites of bone, then refuses to leave (biological half-life measured in decades).
This is a classroom reference range, not an exhaustive list of all oxidation states.
The trap in Cadmium problems
Treating cadmium like its harmless group-mate zinc on safety questions. Chemically parallel, biologically opposite: zinc is essential, cadmium accumulates in kidneys. The itai-itai disease outbreak in Japan traced exactly this Cd2+-for-Ca2+ substitution in bone.
Worked example: Cd in a formula problem
Cd2+ in real compounds
CdCl2
Cadmium chloride
Cd2+ balances chloride ions.
CdO
Cadmium oxide
Cadmium can form oxides where total positive and negative charge balances.
Questions students ask about cadmium
Why were NiCd batteries phased out?
Their anodes cycle cadmium between 0 and +2 effectively, but discarded cells leach Cd2+ into soil and water. EU restrictions pushed consumer batteries to NiMH and lithium chemistries.
What are cadmium quantum dots?
Nanocrystals of CdSe or CdTe (Cd at +2) whose glow color depends purely on particle size. Display makers prized them, then reformulated away from cadmium under toxicity rules.
How does cadmium end up in food?
Plants absorb Cd2+ from soil through the same transporters that carry zinc and iron — rice and leafy greens are efficient collectors. The ion's disguise as a nutrient is precisely the problem.
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.