Tantal kemisk element
Tantalum - Periodic Table of Videos (Kan 2024)
Tantal (Ta), kemisk element, lyst, meget hårdt, sølvgrå metal i gruppe 5 (Vb) i det periodiske system, kendetegnet ved dets høje densitet, ekstremt høje smeltepunkt og fremragende modstand mod alle syrer undtagen hydrofluor ved almindelige temperaturer.
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Tantal forbundet med niob i malm og egenskaber blev tantal opdaget (1802) af den svenske kemiker Anders Gustaf Ekeberg og opkaldt efter den mytologiske karakter Tantalus på grund af det forvirrende problem med at opløse oxidet i syrer. På grund af den store kemiske lighed mellem niob og tantal, var etableringen af de individuelle identiteter af de to elementer meget vanskelig. Tantal blev hurtigt identificeret med niob (dengang kaldet columbium), men i 1844 demonstrerede den tyske kemiker Heinrich Rose deres forskellige karakterer. Selvom noget af det urene metal blev isoleret tidligere, forberedte den russiske kemiker Werner Bolton (1903) den første duktile tantal, som kort blev brugt 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 × 1015flere år; jordtilstanden (den laveste energitilstand) har en halveringstid på kun 8.154 timer.
Elementegenskaber
Atom nummer | 73 |
---|---|
atomvægt | 180,94788 |
smeltepunkt | 2.996 ° C (5.425 ° F) |
kogepunkt | 5.425 ° C (9.797 ° F) |
specifik tyngdekraft | 16,6 ved 20 ° C (68 ° F) |
oxidationstilstande | +2, +3, +4, +5 |
elektronkonfiguration | [Xe] 4f 14 5d 3 6s 2 |
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