Магний силицид

Описание

Magnesium silicide has the molecular formula of Mg₂Si and the molecular weight of 76.6955 g/mol. Its density is 1.998 g/cc and its melting point is 1102°C. It is a black powder.
Mg₂Si crystallizes in a cubic CaF₂ (fluorspar)-type lattice with a = 4.49 ? . The centers of this lattice are analogous to that of diamond. Each Si atom forms four covalent sp3 bonds. The Mg subshells are only half-filled. There is no bonding between the two Mg atom sites. The distance between the Mg and Si atoms is 2.77 ? . Bonding in this compound is essentially covalent.

Химические свойства

Magnesium silicide is a slate blue crystalline solid.

Физические свойства

Magnesium silicide is unstable in air and reacts with moisture to form silane. When magnesium silicide is placed into aqueous HCl, the gas silane, SiH₄, is produced. This gas is the silicon analogue of methane, CH₄, but is more reactive. Silane is pyrophoric, that is due to the presence of O₂ in the air, i.e. it spontaneously combusts in air. These reactions are typical of a Group-2 silicide. Mg₂Si reacts similarly with sulfuric acid. As a powder, magnesium silicide is dark blue or slightly purple in color.

Использование

Magnesium silicide is used to produce alloys such as aluminum alloys. It is also used in food, beverages, as a flavor enhancer and as an intermediate in chemical research.

Общее описание

A colorless crystalline solid. Insoluble in water and denser than water. Contact may irritate skin, eyes and mucous membranes. May be toxic by ingestion.

Реакции воздуха и воды

Contact with moisture under acidic condition generates silanes that ignite in air. Insoluble in water.

Профиль реактивности

MAGNESIUM SILICIDE is a reducing agent. May react vigorously with oxidizing materials.

Угроза здоровью

Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.

Пожароопасность

Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard.

Возможный контакт

Magnesium silicide is used in the semiconductor industry and to produce certain aluminum alloys

Перевозки

UN2624 Magnesium silicide, Hazard Class: 4.3; Labels: 4.3-Dangerous when wet materia

Структура и конформация

The space lattice of Mg2Si belongs to the cubic system, and it has an antifluorite type structure (refer to Mg2Ge) with a lattice constant of a=0.634 nm.

Несовместимости

Possibly pyrophoric, especially in moist air. Pyrophoric; mixtures with air are spontaneously explosive. A strong reducing agent. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, mineral acids, strong acids, strong bases. Reacts with water; releasing explosive hydrogen gas and may also release selfigniting toxic silane gas