Atomic Mass of Dysprosium (Dy)
The relative atomic mass of Dysprosium is 162.50 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
Looking for Dysprosium'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 Dysprosium page is one click away.
Dysprosium by the numbers
One Dysprosium atom carries 66 protons in its nucleus; add the neutrons of its commonest isotope (about 97) and you get its mass number, roughly 163.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 66 |
| Relative atomic mass | 162.50 u |
| Protons | 66 |
| Neutrons (commonest isotope) | 97 |
| Electrons | 66 |
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 (162.50). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Dysprosium a whole number?
No. 162.50 u is the average of Dysprosium'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 Dysprosium have?
Neutrons = mass number − atomic number. For Dysprosium's commonest isotope that is about 163 − 66 = 97, though the exact count differs between isotopes.