Atomic Mass of Ytterbium (Yb)
The relative atomic mass of Ytterbium is 173.05 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
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Ytterbium by the numbers
One Ytterbium atom carries 70 protons in its nucleus; add the neutrons of its commonest isotope (about 103) and you get its mass number, roughly 173.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 70 |
| Relative atomic mass | 173.05 u |
| Protons | 70 |
| Neutrons (commonest isotope) | 103 |
| Electrons | 70 |
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 (173.05). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Ytterbium a whole number?
No. 173.05 u is the average of Ytterbium'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 Ytterbium have?
Neutrons = mass number − atomic number. For Ytterbium's commonest isotope that is about 173 − 70 = 103, though the exact count differs between isotopes.