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Tantalum: the story on HearLore | HearLore
Tantalum
In 1802, Swedish chemist Anders Ekeberg isolated a new element from two mineral samples, one from Sweden and another from Finland, and he named it tantalum after the mythological figure Tantalus. The name was chosen because the metal seemed to mock the chemist, just as Tantalus was mocked by the gods. When Ekeberg immersed the metal in acid, it refused to react, standing knee-deep in the liquid while the acid drained away, eternally tantalizing the scientist with its refusal to be saturated. This chemical inertness became the defining characteristic of the element, a stubborn resistance to corrosion that would eventually make it indispensable to modern industry. The story of its discovery was complicated by the fact that tantalum always occurs in nature alongside niobium, a chemically similar element that had been discovered just one year earlier by Charles Hatchett. For decades, scientists believed they were the same element, a confusion that persisted until the mid-19th century when the true differences between the two were finally unraveled. The name tantalum stuck, a permanent reminder of the metal's frustrating behavior and the ancient Greek punishment that inspired its identity.
The Great Confusion
The history of tantalum is a saga of mistaken identity that spanned nearly sixty years of scientific debate. In 1809, English chemist William Hyde Wollaston compared the oxides of columbium and tantalum, noting their different densities of 5.918 grams per cubic centimeter and 7.935 grams per cubic centimeter, yet he concluded they were identical and kept the name tantalum. This conclusion was supported by Friedrich Wöhler, leading the scientific community to believe that columbium and tantalum were one and the same. The confusion was not resolved until 1846, when German chemist Heinrich Rose argued that there were two additional elements in the tantalite sample, naming them niobium after the daughter of Tantalus and pelopium after his son. The supposed element pelopium was later identified as a mixture of tantalum and niobium, and it was found that niobium was identical to the columbium already discovered in 1801. The differences between the two elements were demonstrated unequivocally in 1864 by Christian Wilhelm Blomstrand and Henri Etienne Sainte-Claire Deville, as well as by Louis J. Troost, who determined the empirical formulas of some of their compounds in 1865. Jean Charles Galissard de Marignac provided further confirmation in 1866, proving that there were only two elements. De Marignac was the first to produce the metallic form of tantalum in 1864, when he reduced tantalum chloride by heating it in an atmosphere of hydrogen. Early investigators had only been able to produce impure tantalum, and the first relatively pure ductile metal was produced by Werner von Bolton in Charlottenburg in 1903. Wires made with metallic tantalum were used for light bulb filaments until tungsten replaced it in widespread use.
Swedish chemist Anders Ekeberg isolated tantalum in 1802 from mineral samples found in Sweden and Finland. He named the element after the mythological figure Tantalus because the metal refused to react when immersed in acid.
When was the difference between tantalum and niobium finally proven?
The distinction between tantalum and niobium was unequivocally demonstrated in 1864 by Christian Wilhelm Blomstrand and Henri Etienne Sainte-Claire Deville. Jean Charles Galissard de Marignac provided further confirmation in 1866 that only two elements existed.
What is the melting point of tantalum and how does it compare to other metals?
Tantalum possesses a melting point of 3017 degrees Celsius which is exceeded among metals only by tungsten, rhenium, and osmium. It is also exceeded by carbon among all elements.
What are the two stable isotopes of natural tantalum and their abundance?
Natural tantalum consists of two stable isotopes 180mTa and 181Ta with 180mTa making up only 0.012 percent of the natural abundance. The isomeric state 180mTa is the only nuclear isomer among primordial nuclides and is the rarest of all.
How is tantalum used in the production of electronic components?
Tantalum powder pressed into a pellet shape serves as one plate of a capacitor with a thin oxide layer acting as the dielectric. This construction allows for high capacitance in a small volume making it attractive for portable telephones and personal computers.
Tantalum is a dark blue-gray transition metal that is dense, ductile, and highly conductive of heat and electricity. It possesses a melting point of 3017 degrees Celsius, which is exceeded among the elements only by tungsten, rhenium, and osmium for metals, and carbon. The metal exists in two crystalline phases, alpha and beta, with the alpha phase being stable at all temperatures up to the melting point and having a body-centered cubic structure. The beta phase is hard and brittle, with a tetragonal crystal symmetry, and it converts to the alpha phase upon heating to 750 to 775 degrees Celsius. Tantalum is highly resistant to corrosion by acids, and at temperatures below 150 degrees Celsius, it is almost completely immune to attack by the normally aggressive aqua regia. It can be dissolved with hydrofluoric acid or acidic solutions containing the fluoride ion and sulfur trioxide, as well as with molten potassium hydroxide. The metal's physical properties make it valuable for laboratory and industrial equipment such as reaction vessels and vacuum furnaces. Its high density and hardness also make it useful for shaping charge and explosively formed penetrator liners, which greatly increase the armor penetration capabilities of a shaped charge. The metal is also used in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, missile parts, heat exchangers, tanks, and vessels.
The Atomic Paradox
Natural tantalum consists of two stable isotopes, 180mTa and 181Ta, with 180mTa making up only 0.012 percent of the natural abundance. This isomeric state, denoted by the m, is predicted to decay in three ways: isomeric transition to the ground state of 180Ta, beta decay to 180W, or electron capture to 180Hf. However, the radioactivity of this nuclear isomer has never been observed, and only a lower limit on its half-life of 2.9 years has been set. The ground state of 180Ta has a half-life of only 8 hours. Among primordial nuclides, 180mTa is the only nuclear isomer and the rarest of all, calculated from the elemental abundance of tantalum and the isotopic abundance of 180mTa within it. Tantalum has been examined theoretically as a salting material for nuclear weapons, where an external shell of tantalum would be irradiated by the intense neutron flux from the weapon, transmuting it into the radioactive isotope 182Ta. The gamma rays from this isotope would significantly increase the radioactivity of the fallout for months. Such salted weapons are not known to have been built, tested, or used. Tantalum is also used as a target material for spallation by high-energy proton beams for the production of a large number of isotopes including 8Li, 80Rb, and 160Yb. The element's unique nuclear properties make it a subject of intense theoretical study, even if its practical application in weaponry remains a hypothetical scenario.
The Conflict Mineral
The major use for tantalum, as the metal powder, is in the production of electronic components, mainly capacitors and some high-power resistors. Tantalum electrolytic capacitors exploit the tendency of tantalum to form a protective oxide surface layer, using tantalum powder, pressed into a pellet shape, as one plate of the capacitor, the oxide as the dielectric, and an electrolytic solution or conductive solid as the other plate. Because the dielectric layer can be very thin, thinner than the similar layer in, for instance, an aluminum electrolytic capacitor, a high capacitance can be achieved in a small volume. Because of the size and weight advantages, tantalum capacitors are attractive for portable telephones, personal computers, automotive electronics and cameras. The metal is also used to produce a variety of alloys that have high melting points, strength, and ductility. Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, missile parts, heat exchangers, tanks, and vessels. Because of its ductility, tantalum can be drawn into fine wires or filaments, which are used for evaporating metals such as aluminum. Tantalum is inert against most acids except hydrofluoric acid and hot sulfuric acid, and hot alkaline solutions also cause tantalum to corrode. This property makes it a useful metal for chemical reaction vessels and pipes for corrosive liquids. Heat exchanging coils for the steam heating of hydrochloric acid are made
The Invisible Capacitor
from tantalum. Tantalum was extensively used in the production of ultra high frequency electron tubes for radio transmitters. Tantalum is capable of capturing oxygen and nitrogen by forming nitrides and oxides and therefore helped to sustain the high vacuum needed for the tubes when used for internal parts such as grids and plates.