Atomic Mass of Platinum (Pt)
The relative atomic mass of Platinum is 195.08 u — the weighted average of its naturally occurring isotopes, on the carbon-12 scale.
Looking for Platinum'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 Platinum page is one click away.
Platinum by the numbers
One Platinum atom carries 78 protons in its nucleus; add the neutrons of its commonest isotope (about 117) and you get its mass number, roughly 195.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 78 |
| Relative atomic mass | 195.08 u |
| Protons | 78 |
| Neutrons (commonest isotope) | 117 |
| Electrons | 78 |
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 (195.08). Exams love this one-mark distinction.
Students also ask
Is the atomic mass of Platinum a whole number?
No. 195.08 u is the average of Platinum'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 Platinum have?
Neutrons = mass number − atomic number. For Platinum's commonest isotope that is about 195 − 78 = 117, though the exact count differs between isotopes.