Physical properties Scandium subgroup

	Sc	Y	La	Ac
density, g/сm3	3.0	4.5	6.2	10.1
tm, oС	1539	1509	920	1050
tb, oС	2727	2927	3469	3300
Rа, nm	0.164	0.181	0.187	0.203
R3+, nm	0.083	0.097	0.104	0.111
Stable nuclides	(100 %)	(100 %)	(99.91 %)	-
Ionisation energy Е ® Е+, kJ∙mol-1
Е+ ® Е2+, kJ∙mol-1
Еo(Е3+ + 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/сm3	4.50	6.45	13.1
tm, oС	1668	1855	2220
tb, oС	3330	4340	4600
	Ti3+/Ti	Zr4+/Zr	Hf4+/Hf
Еo(Е3+ + 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
R5+, nm	0.059	0.066	0.066
Ionisation energy Е0  Е+, еV	6.71	6.88	7.88
density, g/сm3	5.96	8.57	16.6
tm, oС	1900	2470	3015
tb, oС	3400	4760	5500

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.