Atomic Mass of Strontium (Sr)
The relative atomic mass of Strontium is 87.62 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
Teachers call it "one fact, fully handled" — exactly what this page does for Strontium. The answer sits at the top in bold; scroll for the working, the shell-by-shell breakdown and the two questions students ask most. Need the whole picture instead — history, characteristics, uses, exam questions? The full Strontium page is one click away.
Strontium by the numbers
One Strontium atom carries 38 protons in its nucleus; add the neutrons of its commonest isotope (about 50) and you get its mass number, roughly 88.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 38 |
| Relative atomic mass | 87.62 u |
| Protons | 38 |
| Neutrons (commonest isotope) | 50 |
| Electrons | 38 |
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 (87.62). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Strontium a whole number?
No. 87.62 u is the average of Strontium'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 Strontium have?
Neutrons = mass number − atomic number. For Strontium's commonest isotope that is about 88 − 38 = 50, though the exact count differs between isotopes.