Atomic Mass of Zirconium (Zr)
The relative atomic mass of Zirconium is 91.224 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
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Zirconium by the numbers
One Zirconium atom carries 40 protons in its nucleus; add the neutrons of its commonest isotope (about 51) and you get its mass number, roughly 91.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 40 |
| Relative atomic mass | 91.224 u |
| Protons | 40 |
| Neutrons (commonest isotope) | 51 |
| Electrons | 40 |
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 (91.224). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Zirconium a whole number?
No. 91.224 u is the average of Zirconium'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 Zirconium have?
Neutrons = mass number − atomic number. For Zirconium's commonest isotope that is about 91 − 40 = 51, though the exact count differs between isotopes.