What is carbon's oxidation state in CO2 versus CH4?
In CO2, each O is -2, so C = +4. In CH4, each H is +1, so C = -4. Same element, opposite extremes — set by whether carbon's partner pulls electrons harder than it does.
What Is the Charge of Carbon?
Carbon commonly forms C4- C4+ in introductory ionic compounds.
Carbon spans oxidation states from -4 (in CH4) to +4 (in CO2), but it almost never forms actual ions. With four valence electrons, carbon shares rather than transfers — that is the whole reason organic chemistry exists.
| Element | Carbon |
|---|---|
| Symbol | C |
| Atomic number | 6 |
| Common ionic charge | -4, +4 |
| Common ions | C4-, C4+ |
Visual reference
Carbon element image and atomic model
Images are used as visual references; charge rules still depend on the compound.
The electron count behind Carbon's charge
Carbon sits dead center in period 2 with a 2s2 2p2 configuration. Gaining four electrons or losing four are both energetically absurd, so carbon covers the middle ground: four covalent bonds, every time, with the oxidation state depending on how electronegative its partners are.
The classic Carbon error
Writing C4+ or C4- as real ions in ionic compounds. Even in carbides like Al4C3, which we formally treat as containing C4-, the bonding is far from purely ionic. Use the numbers for electron bookkeeping, not as literal charges.
Worked example: C in a formula problem
C4- and C4+ in real compounds
Na4C
sodium carbon compound
Sodium ions can balance C4- in simple ionic examples.
CaC2
calcium carbon compound
Calcium ions can balance common negative Carbon ions.
Questions students ask about carbon
What is the charge of carbon in carbonate, CO3 2-?
The -2 belongs to the whole polyatomic ion, not to carbon. Within carbonate, carbon's oxidation state is +4 (three oxygens at -2 give -6; -6 + 4 = -2 overall).
Why doesn't carbon form a C4+ ion like silicon supposedly does?
Neither does silicon, in truth. Removing four electrons from any small atom takes more energy than bond formation can pay back. Both elements bond covalently instead.
Is diamond charged?
No — diamond is pure carbon at oxidation state 0, every atom sharing four bonds with neighbors. Same for graphite and graphene.
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.