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Technetium

Element 43 · Transition metal

Specimen

Atomic number
43
Atomic mass
[97]
State at room temperature
Solid
Melting point
2,157 °C
Boiling point
4,265 °C
Density
11 g/cm³
Discovered
1937

Mass number of the longest-lived isotope, from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Radioactive. All technetium is radioactive, and it does not occur naturally. Its radiation makes it toxic. Doctors use small amounts of technetium-99m for medical scans. 3

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The atom

Tc
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 13
5 (O) outermost 2
Total43

Configuration [Kr] 4d⁵ 5s²

4d ↑ ↑ ↑ ↑ ↑
5s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 43 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Kr core, with one arrow per electron.

Related elements

Group 7
Mn Manganese Re Rhenium Bh Bohrium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Radioactive Elements .

    Mass number and half-life of the longest-lived isotope of the 34 elements with no standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Royal Society of Chemistry, 2026. Technetium - Element information, properties and uses .

    • A radioactive, silvery metal that does not occur naturally. ... technetium-99m (metastable) is widely used for medical diagnostic studies ... It is toxic due to its radioactivity.