Electron Configuration of Technetium (Tc)
Technetium (Tc, Z = 43) has the electron configuration [Kr] 4d^5 5s^2, filling 5 shells with 2, 8, 18, 13, 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 Technetium page is one click away.
Technetium: every subshell, one by one
The table below unpacks [Kr] 4d^5 5s^2 line by line, so you can watch Technetium's 43 electrons take their seats in order of increasing energy.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Kr] | 0 | 36 |
| 4d | 5 | 41 |
| 5s | 2 | 43 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Technetium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 13 in shell 4, 2 in shell 5. 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 43 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 Technetium that gives [Kr] 4d^5 5s^2.
Students also ask
How many electron shells does Technetium have?
Technetium is in period 5, so its electrons occupy 5 shells, holding 2, 8, 18, 13, 2 electrons respectively.
How many valence electrons does Technetium have?
Its outermost shell holds 2 electrons, so Technetium has 2 valence electrons that take part in bonding.
What is the noble-gas shorthand for Technetium?
The shorthand form is exactly [Kr] 4d^5 5s^2.