Atomic Mass of Copernicium (Cn)
Copernicium has no stable isotope, so no standard atomic weight exists; its most stable isotope has mass number ≈ 285, and the bracketed value [285] marks that estimate.
This is the fast lane: one page, one fact, zero digressions. Read the quick answer, check the table, and if your exam needs the full derivation, the sections below walk through it step by step — in Bangla and English, like every page here. Need the whole picture instead — history, characteristics, uses, exam questions? The full Copernicium page is one click away.
Copernicium by the numbers
One Copernicium atom carries 112 protons in its nucleus; add the neutrons of its commonest isotope (about 173) and you get its mass number, roughly 285.
| Quantity | Value |
|---|---|
| Atomic number (Z) | 112 |
| Relative atomic mass | [285] (no stable isotope) |
| Protons | 112 |
| Neutrons (commonest isotope) | 173 |
| Electrons | 112 |
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 ([285] is shown in brackets because it is only an estimate). Exams love this one-mark distinction.
Why is the mass in brackets?
Every isotope of Copernicium is radioactive and vanishes too quickly to build up a natural mixture — so the IUPAC convention prints the mass number of the longest-lived isotope in square brackets instead of a standard atomic weight.
Students also ask
Is the atomic mass of Copernicium a whole number?
No — Copernicium has no stable isotopes, so chemists use the bracketed estimate [285] rather than a measured average.
How many neutrons does Copernicium have?
Neutrons = mass number − atomic number. For Copernicium's commonest isotope that is about 285 − 112 = 173, though the exact count differs between isotopes.