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Group 3 Elemental Properties

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المصدر:  LibreTexts Project

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30-3-2019

2083

Group 3 Elemental Properties

As shown in Table 1.1, the observed trends in the properties of the group 3 elements are similar to those of groups 1 and 2. Due to their ns²(n − 1)d¹ valence electron configurations, the chemistry of all four elements is dominated by the +3 oxidation state formed by losing all three valence electrons. As expected based on periodic trends, these elements are highly electropositive metals and powerful reductants, with La (and Ac) being the most reactive. In keeping with their highly electropositive character, the group 3 metals react with water to produce the metal hydroxide and hydrogen gas:

2M_(s)+6H₂O_(l)→2M(OH)_3(s)+3H_2(g)

Moreover, all dissolve readily in aqueous acid to produce hydrogen gas and a solution of the hydrated M³⁺(aq) ion. The chemistry of the group 3 metals is almost exclusively that of the M³⁺ ion; the elements are powerful reductants.

The group 3 metals react with nonmetals to form compounds that are primarily ionic in character. For example, reacting group 3 metals with the halogens produces the corresponding trihalides: MX₃. The trifluorides are insoluble in water because of their high lattice energies, but the other trihalides are very soluble in water and behave like typical ionic metal halides. All group 3 elements react with air to form an oxide coating, and all burn in oxygen to form the so-called sesquioxides (M₂O₃), which react with H₂O or CO₂ to form the corresponding hydroxides or carbonates, respectively.

Table 1.1: Some Properties of the Elements of Groups 3

Element	Z	Valence Electron Configuration	Electronegativity	Metallic Radius (pm)	Melting Point (°C)	Density (g/cm3)
Sc	21	4s23d1	1.36	162	1541	2.99
Y	39	5s24d1	1.22	180	1522	4.47
La	57	6s25d1	1.10	183	918	6.15
Ac	89	7s26d1	1.10	188	1051	10.0

Scandium burns readily in oxygen to form scandium (III) oxide, Sc2O3

4Sc_(s)+3O_2(g)→2Sc₂O₃