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. They are used as reducing agents in many chemical industries, they are highly significant in the battery storage technologies such as nickel hydride batteries. Hydrides are classified as following:
- Ionic hydrides – They are formed when hydrogen molecule reacts with most s-block elements which are highly electropositive in nature. In solid state, the ionic hydrides are crystalline, non-conducting and non-volatile. However, in liquid state it conducts electricity. Ionic hydrides on electrolysis liberate hydrogen gas at the anode.
- Covalent hydrides – They are formed when hydrogen molecule reacts with the p block elements. The most common examples, in this case, are CH4 and NH3. The hydrogen compounds formed with non-metals are also called hydrides. They are covalent and volatile compounds. Covalent compounds are further classified as:
\(~~~~~~~~~~~~\) i.electron deficient – when they have few electrons for writing the Lewis \(~~~~~~~~~~~~~~~~\) structure.
\(~~~~~~~~~~~~\) ii.electron-precise – when they have sufficient electrons for writing the Lewis \(~~~~~~~~~~~~~~~~\) structure.
\(~~~~~~~~~~~~\) iii. electrons rich hydrides – when they have excess number of electrons and these \(~~~~~~~~~~~~~~~~\) electrons are represented as lone pairs.
- Interstitial hydrides – They are formed when hydrogen molecule reacts with the d-block and f-block elements, metals of group 7, 8 , 9 do not form hydrides. They do conduct heat and electricity but not to the extent of their parent metals. The lattice of the metal hydrides is different from the parent metal. Transition metals have the ability to absorb hydrogen and this property is used in hydrogenation reactions in order to prepare a large number of compounds. A number of metals can accommodate a large volume of hydrogen and hence they can be used as a storage medium.
So far we have seen what are hydrides and the different types of hydrides, for further details on these topics download Byju’s – the learning app.