Technetium (Tc): Electron Configuration, Properties and Uses
Technetium (Tc): Electron Configuration, Properties and Uses
Electron configuration [Kr] 5s2 4d5 · group 7 · period 5 · Ar [98]
Technetium data
- Atomic number
- 43
- Relative atomic mass
- [98]
- Group
- 7
- Period
- 5
- Block
- d
- Category
- Transition metal
- Electron configuration
- [Kr] 5s2 4d5
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5
- Electrons per shell
- 2, 8, 18, 13, 2 (K L M N O)
- Valence electrons
- 7
- Electronegativity (Pauling)
- 1.9
- First ionisation energy
- 7.28 eV
- Atomic radius (van der Waals)
- 209 pm
- State at room temperature
- Solid
- Melting point
- 2157 °C
- Boiling point
- 4265 °C
- Density
- 11 g/cm³
- Common oxidation states
- +7, +6, +4
- Discovered
- 1937
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 13 · O 2
Orbital diagram (outer electrons)
About technetium
With atomic number 43, technetium (Tc) has 43 protons in its nucleus and 43 electrons as a neutral atom. It is a transition metal in group 7, period 5, d-block. The element was discovered in 1937. Technetium is a solid at room temperature, melting at 2157 °C and boiling at 4265 °C.
Technetium electron configuration
The electron configuration of technetium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5, or in short [Kr] 5s2 4d5. Its electrons occupy 5 shells: K = 2, L = 8, M = 18, N = 13, O = 2. For transition metals, valence electrons are counted from the 5s and 4d subshells: 2 + 5 = 7, matching group 7. When it forms cations, electrons leave the outermost subshell first: Tc4+ = [Kr] 4d3.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d5(43)
Uses of technetium
In industry and the laboratory, technetium turns up in many places, for example medical imaging: Tc-99m is the most widely used diagnostic radioisotope, for example in bone and heart scans.
Safety
Technetium is radioactive. Using, storing or transporting radioactive material requires a licence from the national regulator (BAPETEN in Indonesia). Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 7
Frequently asked questions
What is the electron configuration of technetium?
The electron configuration of technetium (Tc, atomic number 43) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5, or [Kr] 5s2 4d5 in short. By shell: 2, 8, 18, 13, 2.
How many valence electrons does technetium have?
Technetium has 7 valence electrons.
Which group and period is technetium in?
Technetium is in group 7, period 5, d-block.
What is the atomic mass of technetium?
Technetium has no stable isotope, so the mass number of its longest-lived isotope, [98], is given.
Prepare solutions with analytical-grade reagents
AMI Scientific is one of the official TCI distributors in Indonesia. Reagents with lot CoA & SDS, formal quotations and tax invoices for universities and laboratories.
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