Tantalum atomic radius

The most common oxidation state of niobium is +5, although many anhydrous compounds have been made with lower oxidation states, notably +4 and +3, and Nb can be reduced in aqueous solution to Nb by zinc. The aqueous chemistry primarily involves halo- and organic acid anionic complexes. Virtually no cationic chemistry exists because of the irreversible hydrolysis of the cation in dilute solutions. Metal—metal bonding is common. Extensive polymeric anions form. Niobium resembles tantalum and titanium in its chemistry, and separation from these elements is difficult. In the soHd state, niobium has the same atomic radius as tantalum and essentially the same ionic radius as well, ie, Nb Ta = 68 pm. This is the same size as Ti ... 

Calculate the atomic radius of each of the following elements from the data given (a) platinum, fee structure, density 21.450 g-cm 3 (b) tantalum, bcc structure, density 16.654 g-cm-3. 

Identify the element with the larger atomic radius in each of the following pairs (a) vanadium and titanium (b) silver and gold (c) vanadium and tantalum (d) rhodium and iridium. 

Which element of each set has the largest atomic radius (a) nickel, zinc, manganese (b) osmium, platinum, tantalum (c) palladium, tungsten, mercury ... 

The elements all crystallise with the b.c.c. lattice. The small radius of the tantalum atom (inferred from measurements on the metal) is reflected in the high density of the element. The metals all have high m.p. (c/. iron, p. 490). In every transition series the m.p. rise to a maximum at the Gp.VIA element and then fall and, as elements of the third transition series show the highest melting points, the m.p. of tantalum is exceeded by that of few other metals ... 

A similar phenomenon has been observed by the author and Sokolova, 189) for the catalysis of alcohols on pentoxides of vanadium, niobium and tantalum. The increase of dehydration as against dehydrogenation goes on simultaneously with the increase of the atomic radius in the series vanadium (1.36 A) niobium (1.47 A) tantalum (1.49 A.)... 

Calculate the radius of a tantalum (Ta) atom, O given that Ta has a BCC crystal structure, a... 

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