Compounds

Hydrides. Their composition depends on the ratio of components ( — the lack of hydrogen, H₂) and like hydrides of s-elements they can be decomposed by water and oxidised by O₂:

2 + 6 = 2 + 5

+ 3 = + 3

Oxides. The examples of their preparation are shown below:

4Sc + 3O₂ = 2Sc₂О₃

4Y(NO₃)₃ = 2Y₂О₃ + 12NO₂ + 3O₂

They react actively with water. In the series Sc —Y— La—Ac the basic properties of oxides are increased, as well as the rate of their reaction with water,? exothermic heat effect of the reaction.

Hydroxides. In the series Sc(OH)₃—Y(OH)₃—La(OH)₃—Ac(OH)₃ basic properties are also increased. This fact is explained by the M³⁺ size growth and weakening the bond of these ions with hydroxide groups ОН^-. Sc(OH)₃ is an amphoteric hydroxide:

Sc(OH)₃ + 3NaOH = Na₃[Sc(OH)₆]

Oxoscandates are formed when melting Sc₂O₃ or Sc(OH)₃ with alkalis:

Sc₂O₃ + 2NaOH = 2NaScO₂ + H₂O

Y(OH)₃, La(OH)₃ have low solubility in water, although their solutions form weak alkaline medium. For instance, saturated solution of La(OH)₃ absorbs CO₂ from air:

2La(OH)₃ + 3CO₂ ® La₂(CO₃)₃ + 3H₂O

Salts. Solubility of them is close to alkali-earth metals salts solubility. Fluorides MF₃, carbonates М₂(СО₃)₃, phosphates МРО₄ and sulfates M₂(SO₄)₃ are soluble in water.

Scandium forms the most stable coordination compounds with coordination number 6. After scandium it becomes larger and stability of a complex ion decreases. For instance, there are the following aquacomplexes of the Sc subgroup elements: [Sc(H₂O)₆]³⁺, [Y(H₂O)₉]³⁺, [La(H₂O)₉]³⁺. ScF₃ can react with fluorides of alkali metals and form soluble complexes:

ScF₃ + 3KF = K₃[ScF₆]

Carbonates M₂(СO₃)₃ dissolve in saturated carbonates of alkali metals (or ammonium) due to the double salt formation:

K₂CO₃ + La₂(CO₃)₃ ® 2K[La(CO₃)₂]

Halides can be crystalhydrates. Losing water after thermal decomposition, they are transformed to oxohalides:

ScCl₃^.6H₂O ScCl₃^.3H₂O Sc(OH)₂Cl ScOCl

- H₂O - H₂O,-HCl - H₂O

Дата добавления: 2015-07-25