Atomic Mass of Gadolinium (Gd)
The relative atomic mass of Gadolinium is 157.25 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
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Gadolinium by the numbers
One Gadolinium atom carries 64 protons in its nucleus; add the neutrons of its commonest isotope (about 93) and you get its mass number, roughly 157.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 64 |
| Relative atomic mass | 157.25 u |
| Protons | 64 |
| Neutrons (commonest isotope) | 93 |
| Electrons | 64 |
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 (157.25). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Gadolinium a whole number?
No. 157.25 u is the average of Gadolinium'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 Gadolinium have?
Neutrons = mass number − atomic number. For Gadolinium's commonest isotope that is about 157 − 64 = 93, though the exact count differs between isotopes.