The hydrides They are chemical compounds that combine hydrogen atoms (whose oxidation state is, in most cases, -1) and atoms of any other element in the periodic table. For example: sodium hydride, ammonia, silane.
Three categories of hydrides are recognized:
- Metal hydrides. They are those that are formed with metallic elements. They are non-volatile compounds that exhibit conductivity. In these hydrides, hydrogen is found as the hydride ion H–. Within this group, one can distinguish saline hydrides, which form the most electropositive metals (from groups 1 and 2). Saline hydrides are generally white or gray solids that are obtained by direct reaction of metal with hydrogen at high temperatures.
- Volatile or non-metallic hydrides. They are those that are formed with non-metallic elements but little electronegative (nitrogen, phosphorus, arsenic, antimony, bismuth, boron, carbon and silicon). They can also be called molecular or covalent hydrides because they have covalent bonds. They form minerals of quite particular aspects. Silane, a hydride in this group, is generating increasing interest for its value for the manufacture of nanoparticles.
- Hydrogen hydrides. Also called simply hydracids, they correspond to the combination of hydrogen with a halogen (fluorine, chlorine, bromine or iodine) or with an antigenic element (sulfur, selenium, tellurium); in the latter case, hydrogen acts with its positive oxidation number (+1) and the other element is the one that works with a negative oxidation number (-1 in halogens, -2 in amphogens).
Examples of hydrides
- Sodium hydride (NaH)
- Phosphine (PH3)
- Barium hydride (BaHtwo)
- Calcium hydride (CaHtwo)
- Manganese (III) hydride (MnH3)
- Ammonia (NH3)
- Arsine (AsH3)
- Strontium hydride (SrHtwo)
- Hydrobromic acid (HBr(ac))
- Borano (BH3)
- Methane (CH4)
- Silane (SiH₄)
- Hydrofluoric acid (HF(ac))
- Hydrochloric acid (HCl(ac))
- Ferrous hydride (FeHtwo)
- Hydroiodic acid (HI(ac))
- Hydrogen sulfide (HtwoS(ac))
- Selenhydric acid (HtwoI know(ac))
- Tellurhydric acid (HtwoTea(ac))
- Lithium hydride (LiH)
Uses of hydrides
Hydrides are used as desiccants and reducers, and some are used as sources of pure hydrogen.
The calcium hydride It is especially useful as a drying agent for organic solvents. Sodium hydride requires great care in handling, as it reacts violently with water and can ignite.
If a fire should occur due to the ignition of this hydride, do not use water to extinguish it because more flames will be produced. These fires are put out with powder extinguishers.