Technetium (Tc)

Technetium (symbol Tc) is the chemical element with atomic number 43: a transition metal, solid at 0 °C, radioactive, with an atomic mass of 98 u. Discovered in 1937 (Carlo Perrier and Emilio Segrè).

Technetium was the first artificially created element, in 1937, hence its name from the Greek technetos, “artificial.” All its isotopes are radioactive, so it has almost entirely vanished from Earth. Its form technetium-99m is the most widely used tool in nuclear medicine, with tens of millions of scans every year.

Key facts

Atomic number: 43
Symbol: Tc
French name: Technétium
Atomic mass: 98 u
Molar mass: [98] g/mol
Family: Transition metals
Position: period 5, group 7, d-block
State at 0 °C: Solid
Melting point: 2,156.9 °C
Boiling point: 4,264.9 °C
Density: 11 g/cm³
Electronegativity (Pauling): 1.9
First ionization energy: 702 kJ/mol
Atomic radius: 135 pm
Electron configuration: [Kr] 4d⁵ 5s²
Indicative price: 100,000 $/kg (order of magnitude)
Radioactive: yes
Discovery: 1937, Carlo Perrier and Emilio Segrè

Origin of the name

From the Greek technētos, artificial.

What does technetium look like?

A silvery-gray metal that slowly tarnishes in moist air. Very few people have ever seen it in bulk: it is mostly handled in solution, in minute quantities.

Where is technetium found?

Its longest half-life (a few million years) is far too short for it to have survived since Earth formed. Minute traces exist in uranium ores, produced by spontaneous fission. It has also been detected in the light of certain red giant stars.

Natural sources

Pitchblende (minute traces from fission)

How is technetium produced?

Technetium-99 builds up by the tonne in spent nuclear fuel. For medicine, molybdenum-99 is produced by fissioning uranium in research reactors (the Netherlands, Belgium, South Africa, Australia…). It is shipped to hospitals in “generators” where it decays into technetium-99m, which is extracted every day: these devices are nicknamed “technetium cows.”

What is technetium used for?

Bone scans to spot fractures and metastases.
Imaging of the heart, thyroid, lungs and kidneys.
Locating the sentinel lymph node in cancer surgery.
Nuclear waste research (technetium-99).

In everyday life

Hospital nuclear scan
Nuclear cardiac stress test

Role in living things

No biological role. Technetium-99m is ideal for medicine: it emits gamma rays that a camera easily detects, and its 6-hour half-life means it quickly disappears from the body. Depending on the molecule it is attached to, it concentrates in bone, the heart or another organ.

Hazards of technetium

Radioactive: it must be handled in specialized facilities. At the doses used for a medical scan, the exposure is comparable to a few months or years of natural background radiation. Technetium-99, very long-lived (211,000 years), is an issue in nuclear waste management.

Cosmic origin

Human-made: Does not exist (or barely) in nature: synthesized in a reactor or accelerator.

History of technetium

Mendeleev had predicted an “eka-manganese.” After several false discoveries, including “masurium,” announced in 1925 by German chemists, Emilio Segrè and Carlo Perrier identified it in 1937 in Palermo, in a molybdenum foil bombarded in Ernest Lawrence's cyclotron at Berkeley. The name technetium was adopted in 1947.

Did you know?

In 1952, astronomer Paul Merrill detected technetium in red giant stars: since it cannot be old, this proved that stars make elements.
It is the lightest element with no stable isotope.
A single “technetium cow” supplies dozens of scans a day for about a week.
More than 30 million technetium-99m scans are performed worldwide every year.

Isotopes of technetium

No stable isotope at all: it is the lightest element with no stable form. Technetium-99m is the most widely used isotope in medical imaging.

technetium-97: radioactive, half-life 4.21 × 10⁶ years
technetium-98: radioactive, half-life 4.2 × 10⁶ years
technetium-99: radioactive, half-life 211,000 years. Long-lived waste from nuclear reactors.
technetium-99m: radioactive, half-life 6.01 h. Used in tens of millions of scans every year (bone, heart, thyroid).

Related elements

Same family (transition metals): Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Yttrium (Y), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Silver (Ag), Cadmium (Cd), Hafnium (Hf), Tantalum (Ta), Tungsten (W), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt), Gold (Au), Mercury (Hg), Rutherfordium (Rf), Dubnium (Db), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs).

Same column (group 7): Manganese (Mn), Rhenium (Re), Bohrium (Bh).