Scandium subgroup

PHYSICAL PROPERTIES

	Sc	Y	La	Ac
density, g/сm^3	3.0	4.5	6.2	10.1
tm, ^oС
tb, ^oС
Rа, nm	0.164	0.181	0.187	0.203
R^3+, nm	0.083	0.097	0.104	0.111
Stable nuclides	(100 %)	(100 %)	(99.91 %)	-
Ionisation energy Е ® Е^+, kJ∙mol^-1
Е^+ ® Е^2+, kJ∙mol^-1
Е^o(Е^3++ 3е = Е), V	-2.08	-2.37	-2.52	-2.60

Y, La, and Ac are silvery white metals. Sc has a yellowish colour. Sc аnd Y don`t corrode in normal conditions in dry air. La and Ac quickly become dark due to the thin oxide (hydroxide) film formation. Radioactive actinium glowes in the dark with a blue light.

Titanium subgroup

	Ti	Zr	Hf
density, g/сm^3	4.50	6.45	13.1
tm, ^oС
tb, ^oС
	Ti^3+/Ti	Zr^4+/Zr	Hf^4+/Hf
Е^o(Е^3++ 3е = Е), V	-1.76	-1.43	-1.57

Titanium subgroup elements are silvery white malleable metals. Titanium belongs to light metals; Zr and Hf are heavy metals. All are refractory. Pure metals are easily subjected to a mechanical processing. On the other hand, they can be hard and brittle at absorbance of small amounts of О₂ and N₂ (for instance, after thermal processing). Therefore, their welding is only possible using argon-arc method. Ti, Zr, and Hf absorb Н₂ significantly. They form phases of insertion.

Vanadium subgroup

	V	Nb	Ta
Colour	Steel-gray	Light-gray	gray
Rа, nm	0.134	0.146	0.146
R^5+, nm	0.059	0.066	0.066
Ionisation energy Е^0® Е^+, еV	6.71	6.88	7.88
density, g/сm^3	5.96	8.57	16.6
tm, ^oС
tb, ^oС

V, Nb, and Ta are refractory metals with a volume-centred cubic unit cell. Their colour is usually silvery-gray and after oxidation of the surface it becomes dark. The chemical characteristics, properties of Ta and Nb are very similar since practically identical are their ionic and atomic radii. V, Nb, and Ta have high mechanical strength and malleability. When admixtures (O, N, C, B, H and other additives) are present they became brittle and hard because of compounds of varying composition with non-metals that are formed.

Дата добавления: 2015-07-25