Hydrides-Types of Hydrides, Ionic, Covalent, Metallic Hydrides

IUPAC NameHydride
Molecular FormulaH
Molecular Weight1.008 g/mol
Chemical NameHydrogen Anion

What Are Hydrides?

Compounds of hydrogen with less electronegative elements are known as hydrides. So, when hydrogen reacts with any other element, the product formed is considered to be a hydride. If we closely observe the periodic table, hydride formation is not seen from VA group elements, and this condition is known as the hydride gap. Hydrogen molecule usually reacts with many elements except noble gases to form hydrides. However, the properties may vary depending on the type of intermolecular force that exists between the elements, their molecular masses, temperature, and other factors.

Types of Hydrides

Hydrides are mainly divided into three major types or groups. The categories are decided based on what elements the hydrogen forms bonds with or simply on the basis of chemical bonding. The three types of hydrides are ionic, covalent, and metallic hydrides. We will learn about them in detail below.

Ionic or Saline 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.  Saline or ionic hydrides do not dissolve in conventional solvents, and they are mostly used as bases or reducing reagents in organic synthesis.

Example of Ionic Hydrides: Nah, KH, CaH2, etc. They contain hydrogen as the negatively charged (H) ion.

Covalent Hydrides

Covalent hydrides are formed when hydrogen reacts with other similar electronegative elements like Si, C, etc. The most common examples are CH4 and NH3. In general, compounds that are formed when hydrogen is reacted with non-metals are called covalent hydrides. The compounds share a covalent bond and are either volatile or non-volatile compounds. Covalent hydrides are also either liquids or gases.

Example of Covalent Hydrides: SiH4 (silane).

Metallic Hydrides

A hydrogen compound that forms a bond with another metal element is classified as a metal hydride. The bond is mostly covalent type, but sometimes the hydrides are formed with ionic bonds. These are usually formed by transition metals and are mostly non-stoichiometric, hard, high melting and boiling points.

Examples of Metallic Hydrides: TiH aluminium, cadmium, magnesium, etc.

Metal hydrides are also known as interstitial hydrides. They are formed when hydrogen molecule reacts with the d- and f-block elements. Metals of Groups 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 Hydride

  • They are used as reducing agents in many chemical industries.
  • Hydrides are highly significant in battery storage technologies such as nickel hydride batteries.
  • They are used as drying agents.
  • They are used as strong bases in organic synthesis.
  • Metal hydrides are also used for their heat storage, hydrogen storage and compressors capabilities.

Frequently Asked Questions (FAQs)

Q1

What is the formula of hydride?

Hydrides have the general chemical formula H.

Q2

How are hydrides classified?

Hydrides are classified based on the element-hydrogen bonding. For example, if hydrogen is bonded to a metal, metallic hydrides are formed. If hydrogen is bonded to a non-metal, covalent hydrides are formed, and if hydrogen forms a bond with s-block elements, ionic hydrides are formed.

Q3

What happens when ionic hydride reacts with water?

When ionic hydride reacts with water, hydrogen gas is released, and a base is formed. It is a very violent reaction producing fire.

Q4

Is NaH electron deficient?

NaH is not electron deficient. It is an electron-rich metallic hydride.

Q5

What are electron-rich hydrides?

Hydrides which have excess electrons to form bonds are called electron-rich hydrides. For example, NH3 is an electron-rich hydride.

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.