Tc · Element 43 · Manganese group
The first element made by humans rather than found — and the lightest with no stable isotope at all.
Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where technetium sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Size, to scale
Radius 136 pm — that is 0.136 nm, so about 3676 million of them side by side would span a millimetre.
Thermal range
Technetium is liquid over a 2108 K window, from 2430 K to 4538 K.
The story
The first element made by humans rather than found — and the lightest with no stable isotope at all.
Technetium's discovery story spans three-quarters of a century, involving false claims, international rivalry, and the dawn of the nuclear age. Element 43 became chemistry's most elusive prize, with scientists worldwide racing to fill the mysterious gap in the periodic table.
Dmitri Mendeleev's periodic table predicted element 43 should exist between molybdenum and ruthenium, with properties intermediate between these elements. He called this hypothetical element "eka-manganese," predicting its atomic weight and chemical behavior with remarkable accuracy.
Between 1877 and 1925, scientists announced at least four "discoveries" of element 43, each later proven incorrect. German chemist Ida Noddack claimed discovery in 1925, naming the element "masurium" after a region in Prussia, but could never produce convincing evidence.
Italian mineralogist Emilio Segrè initially believed he had found element 43 in platinum ores from South America. However, subsequent analysis proved the samples contained only known elements, adding another false claim to element 43's troubled discovery history.
The true discovery came through nuclear physics, not chemistry. Emilio Segrè, visiting Ernest Lawrence's cyclotron laboratory at Berkeley, received a molybdenum deflector plate that had been bombarded with deuterons for months.
Back in Italy, Segrè and his colleague Carlo Perrier chemically analyzed the irradiated molybdenum using sophisticated separation techniques. They isolated a radioactive fraction with chemical properties exactly matching Mendeleev's predictions for element 43.
Through careful radiochemical analysis, they proved this was genuine element 43 – the first element discovered that does not occur naturally on Earth. They named it "technetium" from the Greek "technetos," meaning "artificial."
Segrè and Perrier's 1937 paper described technetium's chemical behavior in detail, confirming Mendeleev's 66-year-old predictions. The element formed compounds similar to manganese and rhenium, occupied the expected position in the periodic table, and showed the predicted metallic properties.
The first pure technetium metal wasn't isolated until 1962, when researchers at Oak Ridge National Laboratory produced gram quantities through large-scale nuclear reactor operations. This pure metal confirmed technetium's predicted physical properties, including its silvery appearance and high melting point.
Segrè's discovery of technetium contributed to his 1959 Nobel Prize in Physics (shared with Owen Chamberlain for discovering the antiproton). The technetium discovery demonstrated that nuclear physics could create entirely new elements, opening the door to discovering the transuranium elements.
Technetium's discovery proved that the periodic table could be extended through human ingenuity, inspiring the creation of elements 93-118. It also launched the field of nuclear medicine, as technetium-99m became the most widely used medical radioisotope within two decades of the element's discovery.
The technetium discovery exemplified international scientific cooperation during a tense political period. American cyclotron technology, Italian radiochemistry expertise, and global scientific communication combined to solve one of chemistry's greatest mysteries.
Applications
Technetium-99m is the workhorse of nuclear medicine, used in over 20 million medical procedures annually worldwide. This remarkable isotope has a perfect 6-hour half-life – long enough for complex medical procedures but short enough to minimize radiation exposure to patients.
Technetium-99m MIBI (sestamibi) scans reveal blocked coronary arteries with extraordinary precision, helping cardiologists diagnose heart disease before heart attacks occur. These scans can detect artery blockages as small as 2mm in diameter, potentially saving millions of lives through early intervention.
Technetium bone scans detect cancer metastases months before they appear on X-rays or CT scans. Oncologists use these scans to stage cancer progression and monitor treatment effectiveness, making technetium an essential tool in the global fight against cancer.
Technetium-99m HMPAO crosses the blood-brain barrier, allowing doctors to image brain blood flow and detect strokes, dementia, and epilepsy. These scans provide crucial information for treating neurological conditions affecting millions of patients worldwide.
Cutting-edge research uses technetium-based compounds to detect amyloid plaques in living brains, potentially enabling Alzheimer's diagnosis years before symptoms appear. This early detection could revolutionize dementia treatment and prevention.
Technetium's unique radioactive properties make it invaluable for scientific research. Its predictable decay patterns and gamma ray emissions provide researchers with a precise tool for studying biological processes and chemical reactions.
Researchers use technetium as a tracer to study environmental contamination, industrial processes, and biological systems. Technetium's artificial origin means any detected technetium must come from human activities, making it an ideal environmental monitoring tool.
Long-lived technetium-99 (half-life: 211,000 years) is both a challenge and an opportunity in nuclear waste management. Researchers are developing methods to transmute this long-lived isotope into shorter-lived or stable elements, potentially solving one of nuclear power's most persistent problems.
Technetium serves as an indicator of nuclear reactor performance and safety. Its presence and concentration in reactor systems provide early warning of fuel rod damage or containment breaches, enhancing nuclear safety protocols worldwide.
Technetium's unique properties as a corrosion inhibitor show promise for protecting steel in extreme environments. Even tiny amounts (1-10 parts per million) can dramatically reduce steel corrosion in seawater and acidic conditions.
Research continues into technetium's potential applications in advanced materials, electronics, and space exploration. As the first artificially produced element, technetium represents humanity's ability to create new materials for solving future challenges.
Though invisible to patients, technetium-99m is present in numerous routine medical procedures. Every major hospital worldwide maintains technetium generators, making this artificial element more common in medical facilities than many naturally occurring elements.
Emergency rooms rely on technetium scans for rapid diagnosis of life-threatening conditions. A technetium lung scan can diagnose a pulmonary embolism in 30 minutes, compared to hours for traditional tests – potentially saving lives through faster treatment.
Children receive technetium scans to diagnose kidney problems, bone infections, and congenital abnormalities. The isotope's short half-life minimizes radiation exposure to growing bodies while providing crucial diagnostic information.
Hospital nuclear pharmacies prepare dozens of different technetium-based radiopharmaceuticals daily. These specialized medications target specific organs and tissues, enabling precise medical imaging with minimal side effects.
Medical students, residents, and technologists learn nuclear medicine procedures using technetium-based phantoms and training materials. This hands-on education ensures safe and effective use of nuclear medicine technologies worldwide.
Pharmaceutical companies use technetium in developing new medical imaging agents. Research into technetium-labeled antibodies and peptides promises even more precise disease detection and treatment monitoring.
Ongoing clinical trials investigate technetium's potential for imaging new diseases and conditions. These studies may expand technetium's medical applications to include molecular imaging of cancer, heart disease, and neurological disorders.
International aid organizations use portable technetium generators to bring nuclear medicine to underserved regions. These mobile units enable life-saving diagnostic procedures in areas lacking traditional medical infrastructure.
Emergency medical teams deploy technetium imaging equipment during natural disasters and humanitarian crises, providing rapid diagnosis capabilities when traditional hospitals are unavailable or overwhelmed.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
Technetium holds the unique distinction of being the first element discovered that does not occur naturally on Earth. Every technetium atom on our planet has been artificially created by human technology, making it literally a "man-made" element.
For decades, element 43 represented a mysterious gap in the periodic table. Scientists knew it should exist based on Mendeleev's periodic law, but no one could find it in nature. This absence puzzled chemists and led to numerous false discovery claims before the truth became clear.
Technetium does form naturally in the cores of red giant stars through neutron capture processes. However, its relatively short half-life (the longest-lived isotope lasts only 4.2 million years) means that any primordial technetium formed during Earth's creation has long since decayed away.
Astronomers detect technetium's spectral signature in the atmospheres of S-type stars, providing direct evidence of active nucleosynthesis. These stellar observations helped confirm theories about how heavy elements form in stellar interiors.
Today, technetium is produced in nuclear reactors through the fission of uranium-235. When uranium atoms split, they produce a variety of fission fragments, including molybdenum-99, which decays to technetium-99m with a 66-hour half-life.
Technetium-99 is one of the most problematic components of nuclear waste due to its 211,000-year half-life. Nuclear waste repositories worldwide contain tons of technetium-99, representing humanity's largest artificial concentration of this element.
Unlike many radioactive waste components, technetium forms highly mobile pertechnetate ions (TcO4-) that can travel through groundwater. This mobility makes technetium a key concern for nuclear waste storage and environmental monitoring.
Scientists can produce technetium through several artificial methods, including neutron bombardment of molybdenum, deuteron bombardment of molybdenum, and extraction from nuclear fuel waste. Each method produces different technetium isotopes with varying properties and half-lives.
Particle accelerators can produce technetium-99m directly by bombarding molybdenum-100 targets with protons. This method offers an alternative to reactor-based production and could help address supply shortages for medical applications.
If Earth's 4.5-billion-year history were compressed into a single year, all naturally occurring technetium would have disappeared by February. Every technetium atom on Earth has been created within the last 80 years of human nuclear technology.
Handling
Technetium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Technetium's primary safety concern is radiation exposure, not chemical toxicity. All technetium isotopes are radioactive, requiring specialized handling procedures, monitoring equipment, and training for safe use.
Technetium-99m's 6-hour half-life and low-energy gamma rays make it one of the safest medical radioisotopes. Patient radiation doses are typically lower than annual background radiation, but proper protocols still ensure maximum safety.
Healthcare workers handling technetium must follow strict radiation safety protocols. Nuclear medicine departments maintain comprehensive safety programs including training, monitoring, and emergency procedures.
While radiation is the primary concern, technetium's chemical toxicity resembles that of rhenium and manganese. Studies suggest moderate chemical toxicity, but radiation exposure limits are always more restrictive than chemical exposure limits.
Technetium-99: The long-lived isotope (211,000-year half-life) poses greater long-term risks due to persistent internal contamination. Environmental exposure should be minimized through proper waste management.
Technetium waste requires specialized disposal procedures based on isotope half-life and activity levels. Short-lived technetium-99m can be stored for decay, while long-lived technetium-99 requires permanent disposal in licensed facilities.
Facilities using technetium must monitor air, water, and surface contamination. Environmental release limits ensure public safety while allowing beneficial medical and research applications.
Quick answers
Technetium (symbol Tc) is element 43 on the periodic table, a transition metal in period 5, group 7. The first element made by humans rather than found — and the lightest with no stable isotope at all. At room temperature it is a solid, and it is radioactive.
[Kr] 4d⁵ 5s², giving 5 occupied shells holding 2, 8, 18, 13, 2 electrons respectively.Technetium melts at 2430 K (2156.9 °C) and boils at 4538 K (4264.9 °C). That puts it among the most refractory elements — it stays solid at temperatures that vaporise most metals.
Technetium has no stable isotope, so it has no standard atomic weight. The figure quoted, 98, is the mass number of its longest-lived known isotope.
Technetium has a density of 11 g/cm³. Water is 1.0 g/cm³, so a block of technetium is about 11× heavier.
Technetium has a Pauling electronegativity of 1.9. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Technetium was discovered in 1937 by Perrier & Segre. It is named after greek technetos, "artificial" — the first synthetic element.
Technetium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Technetium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.