Write the formula for iron(III) sulfide.
Fe3+ and S2-. Cross to a common multiple of 6: two Fe3+ (+6) and three S2- (-6) give Fe2S3.
What Is the Charge of Sulfur?
Sulfur commonly forms S2- S4+ S6+ in introductory ionic compounds.
Sulfur's ionic charge is 2-: the sulfide ion S2- in FeS2 (fool's gold) and H2S (rotten-egg gas). Bonded to oxygen it goes positive — +4 in sulfite (SO3 2-) and sulfur dioxide, +6 in sulfate (SO4 2-) and battery acid H2SO4.
| Element | Sulfur |
|---|---|
| Symbol | S |
| Atomic number | 16 |
| Common ionic charge | -2, +4, +6 |
| Common ions | S2-, S4+, S6+ |
Visual reference
Sulfur element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
The electron count behind Sulfur's charge
Sulfur sits directly below oxygen with a [Ne]3s2 3p4 configuration, two electrons short of argon — hence 2- with metals. Unlike oxygen, though, sulfur has empty 3d orbitals nearby, letting it form four or six bonds to oxygen and climb to +4 and +6.
The classic Sulfur error
Confusing sulfide (S2-), sulfite (SO3 2-), and sulfate (SO4 2-). All carry 2-, so formulas look interchangeable — but CaS, CaSO3, and CaSO4 are three different substances (a flotation agent, a preservative byproduct, and gypsum wallboard).
Worked example: S in a formula problem
S2- and S4+ and S6+ in real compounds
Na2S
sodium sulfur compound
Sodium ions can balance S2- in simple ionic examples.
CaS
calcium sulfur compound
Calcium ions can balance common negative Sulfur ions.
Questions students ask about sulfur
What is the charge of sulfur in H2SO4?
+6, sulfur's maximum. Two H (+2) and four O (-8) require sulfur at +6 for neutrality. Concentrated sulfuric acid's hunger for electrons at that state is what makes it so aggressive.
Why does sulfur smell — is that the S2- ion?
The famous smells are covalent molecules: H2S (rotten eggs) and organic thiols (skunk). In them sulfur is at -2 oxidation state, but they are gases and liquids, not ionic salts.
Can sulfur really form six bonds? Doesn't that break the octet rule?
In SF6 and sulfate, sulfur is surrounded by six bonding pairs. Period 3 elements have the orbital room to exceed eight shared electrons — one reason the octet rule is a guideline, not a law.
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.