Technetium

Technetium is a radioactive metallic element with the symbol Tc and atomic number 43, belonging to Group 7 of the periodic table. It holds a distinctive place in chemistry as the first element to be artificially produced, bridging the gap between manganese and rhenium. Despite its scarcity in nature, technetium has gained significant industrial and medical relevance, particularly in nuclear medicine, corrosion prevention, and scientific instrumentation.
Although invisible in everyday life, technetium’s impact is profound — most notably through its isotope technetium-99m (Tc-99m), which is used in millions of diagnostic medical scans annually. This single isotope represents one of the most important tools in modern healthcare, while other forms of technetium contribute to technological and research advancements.

Discovery and Characteristics

The quest to find element 43 began in the 19th century when chemists noticed an apparent gap between molybdenum and ruthenium in the periodic table. It was not until 1937 that Carlo Perrier and Emilio Segrè successfully identified and isolated technetium from molybdenum bombarded by deuterons in a cyclotron at the University of California, Berkeley. The name technetium derives from the Greek technetos, meaning “artificial”, reflecting its synthetic origin.
Physically, technetium is a silvery-grey metal that tarnishes slowly in moist air. It exhibits chemical properties intermediate between those of rhenium and manganese. It forms multiple oxidation states, ranging from −1 to +7, with the +4 and +7 states being the most stable.
Technetium has a melting point of 2157°C and a boiling point of 4265°C, indicating strong metallic bonding. It is a poor conductor of heat and electricity compared with most transition metals, a property influenced by its radioactive nature.

Occurrence and Production

Technetium is extremely rare in nature, existing only in trace amounts in uranium ores as a fission product. Its natural abundance is less than one part per trillion in the Earth’s crust. Most technetium is produced artificially as a by-product of uranium fission in nuclear reactors.
The isotope technetium-99 is generated during the reprocessing of spent nuclear fuel, where uranium-235 splits into various fission fragments, including technetium isotopes. For medical and industrial purposes, technetium-99m is obtained from the decay of molybdenum-99 (Mo-99), which is produced in research reactors.

Isotopes and Radioactivity

Technetium has no stable isotopes, making it unique among light transition metals. There are around 30 known isotopes, with mass numbers ranging from 85 to 118. The most significant are:

• Technetium-99m (Tc-99m): The metastable form of technetium-99, with a half-life of 6 hours, used extensively in nuclear medicine for diagnostic imaging.
• Technetium-99 (Tc-99): The ground state of technetium-99, with a half-life of 211,000 years, used for research and industrial applications.
• Technetium-97 and Technetium-98: Short-lived isotopes with limited use in experimental studies.

Because of its radioactivity, technetium emits low-energy gamma rays and beta particles, which can be safely detected and controlled under proper shielding conditions.

Industrial and Technological Applications

While technetium’s most famous role lies in medicine, it also serves niche industrial functions in materials science, corrosion resistance, and analytical chemistry.

• Corrosion Inhibitors: Technetium, particularly TcO₄⁻ (pertechnetate ion), has been used in small concentrations as a corrosion inhibitor for steel. A thin technetium oxide layer prevents oxidative degradation in closed water and chemical systems. This property was extensively studied for use in nuclear reactors and power generation systems, where long-term metal integrity is crucial. However, due to concerns over radioactivity and disposal, practical applications have largely been replaced by safer alternatives.
• Scientific Research and Calibration: Technetium isotopes are used to calibrate radiation detectors and to study the behaviour of fission products in nuclear fuels. Because technetium-99 is one of the most abundant long-lived fission by-products, understanding its chemical interactions helps scientists improve nuclear waste management and radiation safety protocols.
• Catalysis: Some laboratory experiments suggest that technetium compounds may function as effective catalysts in hydrogenation and oxidation reactions, similar to rhenium-based catalysts. However, due to safety and economic limitations, such applications remain confined to research.

Everyday and Medical Applications

Technetium’s most visible and vital contribution to everyday life comes through its role in medical diagnostics. The radioisotope technetium-99m has transformed nuclear medicine, providing detailed imaging of internal organs and physiological processes without the need for invasive procedures.

• Nuclear Medicine Imaging: Technetium-99m is used in over 30 million medical procedures worldwide each year, making it the most widely used radioisotope in medicine. It is incorporated into radiopharmaceutical compounds that target specific organs, allowing clinicians to visualise structures and functions using gamma cameras.
  Key diagnostic applications include:
  • Bone scans: Detection of fractures, tumours, and infections.
  • Cardiac imaging: Assessment of blood flow and heart function.
  • Lung scans: Evaluation of pulmonary embolism and ventilation–perfusion balance.
  • Kidney and liver scans: Measurement of organ function and blood filtration rates.
  • Thyroid and brain imaging: Examination of metabolic and neurological activity.

  The isotope’s short half-life ensures rapid decay, minimising radiation exposure to patients while providing high-resolution imaging data.

• Medical Research: Technetium isotopes are used to develop and test new radiopharmaceuticals, contributing to advancements in targeted cancer therapy, neurology, and cardiology.

Economic and Strategic Importance

Technetium’s economic significance lies primarily in its medical isotope production chain. The global market for Tc-99m radiopharmaceuticals is valued in billions of pounds, forming the backbone of nuclear medicine diagnostics.

• Production Centres: Technetium-99m is not produced directly but is derived from molybdenum-99, which is generated in a handful of research reactors located in Canada, the Netherlands, South Africa, Australia, and Belgium. This limited production network makes isotope supply a strategic concern for healthcare systems worldwide.
• Reactor and Supply Economics: Periodic shutdowns or maintenance at isotope-producing reactors have historically caused global shortages of Tc-99m, underscoring its importance in the medical economy. Efforts are underway to develop accelerator-based production methods using low-enriched uranium to ensure stable, sustainable isotope supplies.
• Industrial By-product Management: As a fission product in nuclear reactors, technetium-99 contributes to nuclear waste management costs. Research into immobilising technetium within glass or ceramic matrices aims to reduce long-term environmental and economic risks associated with waste disposal.

Environmental and Safety Considerations

Because of its radioactive nature, technetium requires careful handling and long-term containment. The isotope Tc-99 poses environmental challenges due to its long half-life and mobility in water as the pertechnetate ion (TcO₄⁻), which does not bind strongly to soil or minerals.
In nuclear waste management, technetium is one of the most persistent radionuclides. Modern strategies aim to:

• Immobilise it in stable solid forms (e.g., borosilicate glass).
• Reduce Tc⁷⁺ to less soluble oxidation states.
• Incorporate it into crystalline ceramic phases for geological storage.

In medical contexts, Tc-99m is handled in microgram quantities and decays rapidly, posing negligible risk to patients and medical staff under regulated protocols.

Research and Emerging Applications

Research continues to explore new ways of utilising technetium’s unique nuclear and chemical characteristics:

• Radiopharmaceutical Innovation: Development of new Tc-99m compounds for imaging cancer biomarkers, brain receptors, and cardiovascular function.
• Alternative Production Methods: Particle accelerator technologies and linear accelerators are being developed to reduce reliance on uranium-based reactors.
• Nuclear Waste Transmutation: Experimental systems investigate converting Tc-99 into stable isotopes through neutron bombardment, potentially reducing long-lived waste hazards.
• Nanotechnology and Materials Science: Studies explore technetium’s potential in surface coatings and advanced alloys, leveraging its corrosion-resistant oxides.

Everyday Relevance

Though most people never see technetium directly, its influence is pervasive in modern life:

• Hospitals depend on Tc-99m imaging to diagnose millions of patients annually.
• Power generation and research reactors manage technetium as part of their nuclear material cycle.
• Scientific instruments use technetium isotopes to test and calibrate radiation detection systems.

Technetium’s presence ensures safer medical care, more efficient nuclear technology, and deeper understanding of radioactive materials, making it one of the most practically significant synthetic elements ever created.