Atomic Mass of Krypton (Kr)
The relative atomic mass of Krypton is 83.798 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
Looking for Krypton'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 Krypton page is one click away.
Krypton by the numbers
One Krypton atom carries 36 protons in its nucleus; add the neutrons of its commonest isotope (about 48) and you get its mass number, roughly 84.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 36 |
| Relative atomic mass | 83.798 u |
| Protons | 36 |
| Neutrons (commonest isotope) | 48 |
| Electrons | 36 |
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 (83.798). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Krypton a whole number?
No. 83.798 u is the average of Krypton'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 Krypton have?
Neutrons = mass number − atomic number. For Krypton's commonest isotope that is about 84 − 36 = 48, though the exact count differs between isotopes.