Element 43 · Transition metal
Technetium (Tc) — Element 43
Greek technetos — artificial
Technetium (Tc) is a transition metal in Period 5, Group 7 of the periodic table with atomic number 43, standard atomic weight [98] u, and ground-state electron configuration [Kr] 4d⁵ 5s². At standard temperature and pressure it is classified as a short-lived synthetic nuclide with 7 valence electrons and common oxidation states +7, +4.
Medical imaging (Tc-99m)
What are the atomic properties and physical constants of Technetium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 43
- Standard atomic mass
- [98] u
- Chemical family
- Transition metal
- Ground-state configuration
- [Kr] 4d⁵ 5s²
- Electrons per shell
- 2, 8, 18, 13, 2
- Valence electrons
- 7
- Common ion charges / oxidation states
- +7, +4
- Phase at STP
- Synthetic
- Pauling electronegativity
- 1.90 Pauling
- First ionization energy
- 702 kJ/mol
- Atomic radius
- 183 pm
- Melting point
- 2,157 °C
- Boiling point
- 4,265 °C
- Discovery year
- 1937
- Table coordinate
- Period 5, Group 7
- Radioactivity
- Radioactive (no stable isotopes)
How are electrons arranged across Technetium’s shells?
A neutral Technetium atom contains 43 electrons distributed across 5 occupied principal energy shells ([Kr] 4d⁵ 5s²). The table below compares Technetium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Tc | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 18 e⁻ | 18 e⁻ |
| n = 4 | N | 13 e⁻ | 32 e⁻ |
| n = 5 | O | 2 e⁻ | 50 e⁻ |
Frequently Asked Questions about Technetium (Tc)
What is the atomic mass and atomic number of Technetium (Tc)?
Technetium (Tc) has atomic number Z = 43 (43 protons in its nucleus) and an IUPAC standard atomic weight of [98] u. It sits in Period 5, Group 7 and is classified as a transition metal.
What is the ground-state electron configuration of Technetium?
The neutral ground-state electron configuration of Technetium (Z = 43) is [Kr] 4d⁵ 5s². Across its 5 occupied principal shells (n = 1 to n = 5), the electrons per shell are 2, 8, 18, 13, 2, with 7 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Technetium?
Technetium commonly forms +7, +4 oxidation states or ion charges in compounds. Its Pauling electronegativity is 1.90 and its first ionization energy is 702 kJ/mol.
When was Technetium discovered and what is it used for?
Technetium was discovered in 1937 (Greek technetos — artificial). Medical imaging (Tc-99m)
How does Technetium compare to neighboring elements?
Other transition metal elements: