Electron Configuration of Fermium (Fm)
Fermium (Fm, Z = 100) has the electron configuration [Rn] 5f^12 7s^2, filling 7 shells with 2, 8, 18, 32, 30, 8, 2 electrons.
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 Fermium page is one click away.
Fermium: every subshell, one by one
The table below unpacks [Rn] 5f^12 7s^2 line by line, so you can watch Fermium's 100 electrons take their seats in order of increasing energy.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Rn] | 0 | 86 |
| 5f | 12 | 98 |
| 7s | 2 | 100 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Fermium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 30 in shell 5, 8 in shell 6, 2 in shell 7. The outermost shell holds 2 electrons — the ones that do all the bonding.
How to derive it yourself
Follow the aufbau order (1s → 2s → 2p → 3s → 3p → 4s → 3d → …), pouring 100 electrons into orbitals of capacity 2 (s), 6 (p), 10 (d) and 14 (f) until none remain. Write the filled inner shells as the nearest noble-gas core — for Fermium that gives [Rn] 5f^12 7s^2.
Students also ask
How many electron shells does Fermium have?
Fermium is in period 7, so its electrons occupy 7 shells, holding 2, 8, 18, 32, 30, 8, 2 electrons respectively.
How many valence electrons does Fermium have?
Its outermost shell holds 2 electrons, so Fermium has 2 valence electrons that take part in bonding.
What is the noble-gas shorthand for Fermium?
The shorthand form is exactly [Rn] 5f^12 7s^2.