Tantal (Ta), kjemisk element, lyst, veldig hardt, sølvgrått metall fra gruppe 5 (Vb) i det periodiske bordet, preget av dets høye tetthet, ekstremt høye smeltepunkt, og utmerket motstand mot alle syrer unntatt hydrofluor ved vanlige temperaturer.
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Periodisk tabellquiz
Mt
Nært assosiert med niob i malmer og egenskaper, ble tantal oppdaget (1802) av den svenske kjemikeren Anders Gustaf Ekeberg og oppkalt etter den mytologiske karakteren Tantalus på grunn av det pirrende problemet med å løse opp oksydet i syrer. På grunn av den store kjemiske likheten mellom niob og tantal, var etablering av de individuelle identitetene til de to elementene veldig vanskelig. Tantal ble snart identifisert med niob (den gang kalt columbium), men i 1844 demonstrerte den tyske kjemikeren Heinrich Rose deres distinkte karakterer. Selv om noe av det urene metallet ble isolert tidligere, forberedte den russiske kjemikeren Werner Bolton (1903) den første duktile tantal, som ble brukt kort som glødelampe.
Relatively rare, tantalum is about as abundant as uranium. It occurs, with niobium, in the columbite–tantalite series (in which columbite [FeNb2O6] and tantalite [FeTa2O6] occur in highly variable ratios) and the pyrochlore–microlite series of minerals. Native tantalum metal with some niobium and traces of manganese and gold occurs sparingly in Russia in placers in the Ural Mountains and possibly the Altai Mountains in Central Asia. Rwanda is the world’s largest extractor of tantalum. (For mineralogical properties, see native element [table].)
Tantalum is separated from niobium compounds by solvent extraction in a liquid-liquid process and is then reduced to metallic tantalum powder. The massive metal is produced by powder metallurgy techniques. It can also be obtained by either electrolysis of fused salts or reduction of fluoro complexes with a very reactive metal such as sodium. The most important uses for tantalum are in electrolytic capacitors and corrosion-resistant chemical equipment. Tantalum capacitors have the highest capacitance per unit volume of any capacitors and are used extensively in miniaturized electrical circuitry. Other uses include getters and components in electron tubes, rectifiers, and prosthetic devices.
Tantalum is chemically much like niobium because both have similar electronic configurations and because the radius of the tantalum ion is nearly the same as that of niobium as a result of the lanthanoid contraction. Tantalum is usually in the +5 oxidation state in its compounds; lower oxidation states, especially from +2 to +4, have been prepared. Tantalum compounds are relatively unimportant commercially, although the carbide TaC is used in cemented-carbide tools for machining hard metals. Nearly all naturally occurring tantalum is in one stable isotope, tantalum-181. However, a small amount, 0.012 percent, is tantalum-180, which has the unusual property of being found in its excited state. The tantalum-180 excited state has a half-life of more than 1.2 × 1015år; grunntilstanden (den laveste energitilstanden) har en halveringstid på bare 8.154 timer.
Elementegenskaper
| atomnummer | 73 |
|---|---|
| atomvekt | 180,94788 |
| smeltepunkt | 2,996 ° C (5,425 ° F) |
| kokepunkt | 5,425 ° C (9,797 ° F) |
| spesifikk tyngdekraft | 16,6 ved 20 ° C |
| oksidasjonstilstander | +2, +3, +4, +5 |
| Elektronkonfigurasjon | [Xe] 4f 14 5d 3 6s 2 |
