Atomic Mass of Carbon (C)
The relative atomic mass of Carbon is 12.011 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
Looking for Carbon's atomic mass without wading through a whole chapter? Here is the direct answer first, then the tables and derivations examiners want to see. Every number on this page comes from the same engine that powers the interactive table. Need the whole picture instead — history, characteristics, uses, exam questions? The full Carbon page is one click away.
Carbon by the numbers
One Carbon atom carries 6 protons in its nucleus; add the neutrons of its commonest isotope (about 6) and you get its mass number, roughly 12.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 6 |
| Relative atomic mass | 12.011 u |
| Protons | 6 |
| Neutrons (commonest isotope) | 6 |
| Electrons | 6 |
Atomic mass vs mass number
Mass number (A) counts particles — protons + neutrons in one specific atom, always a whole number. Relative atomic mass is the experimentally measured average over all natural isotopes, so it comes out fractional (12.011). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Carbon a whole number?
No. 12.011 u is the average of Carbon's natural isotopes, which is why it lands between whole numbers. The mass number of a single isotope, though, is always whole.
How many neutrons does Carbon have?
Neutrons = mass number − atomic number. For Carbon's commonest isotope that is about 12 − 6 = 6, though the exact count differs between isotopes.