What are Hydrides?
Compounds of hydrogen with less electronegative elements are known as Hydrides. In periodic table Hydrides formation is not seen from VA group elements hence it is known as hydride gap.
Hydrogen molecule reacts with many elements except the noble gases to form hydrides. An element Y when reacts with hydrogen forms YHx , for example, MgH2. Hydride is actually an anion of hydrogen.
Types of Hydrides
On the basis of chemical bonding, hydrides are of following types.
Ionic or Salt like Hydrides
They are formed when hydrogen molecule reacts with highly electropositive s-block elements (Alkali Metals and Alkaline Earth Metals). In solid state, the ionic hydrides are crystalline, non-conducting and non-volatile. However, in a liquid state, they conduct electricity. Ionic hydrides on electrolysis liberate hydrogen gas at the anode.
Example of Ionic Hydrides: Nah, KH, CaH2, etc. These contain the H– ion.
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These are hard and formed by hydrogen and other similar electronegative elements like Si, C, etc. The most common examples are CH4 and NH3. The hydrogen compounds formed with non-metals are also called hydrides. They are covalent and volatile compounds.
Example of Covalent Hydrides: SiH4 (silane)
These are formed by transition metals. These are mostly non-stoichiometric, hard, high melting and boiling points.
Example of Metallic Hydrides: TiH.
They are formed when hydrogen molecule reacts with the d- and f-block elements. Metals of group 7, 8, and 9 do not form hydrides. They do conduct heat and electricity but not to the extent of their parent metals.
Uses of Hydrides
They are used as reducing agents in many chemical industries. Hydrides are highly significant in battery storage technologies such as nickel hydride batteries.