Technetium (Tc)
[Kr] 4d⁵ 5s². 5 unpaired electrons, period 5, group 7, d block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
TcTechnetium, Z = 43, [98] u
[Kr] 4d5 5s2
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s²
- Blockd block
- Period5
- Group7
- Valence7
- Unpaired5
- MagneticPara
Last electron 4d
- n4shell
- l2d subshell
- m+2orbital
- s+½spin up
Step by step
- Technetium has 43 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁵.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s².
- Replace the krypton core with [Kr]: [Kr] 4d⁵ 5s².
Technetium (Tc): the numbers
| Atomic number | 43 |
|---|---|
| Atomic mass | [98] u |
| Period | 5 |
| Group | 7 |
| Block | d block |
| Valence electrons | 7 |
| Unpaired electrons | 5 |
| Magnetic | paramagnetic |
| Last electron | 4d: n = 4, l = 2, m = +2, s = +1/2 |
Technetium (Tc): quick answers
What is the electronic configuration of technetium?
Technetium has 43 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s², or [Kr] 4d⁵ 5s² in short.
How many unpaired electrons does technetium have?
Technetium has 5 unpaired electrons, so it is paramagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of technetium?
The last electron goes into 4d: n = 4, l = 2, m = +2, s = +1/2. Orbitals fill from m = −l up, spin +½ first.