Hydride Definition Types Properties and Reactions Explained
Hydride is an anion for the hydrogen atom. The hydrogen can potentially react with different elements of the periodic table. The Nucleophilic, basic, and reducing properties are found in chemical compounds of hydrogen, and hydride. The hydride compounds are formed using all elements of the periodic table, with the exception of the few noble gases.
Hydrides
Based on the bond formed with the Hydride ions, and the element, the properties of the specific hydride compound can be explained. The molecular formula is H and the molecular weight is about 1.008 g/mol. It has been observed that hydrogen atoms do not react with VA group elements in the periodic table. This is referred to as the hydride gap.
The Different Types of Hydrides
Based on the type of elements that can react with hydrogen atoms, and the chemical bonds, the hydrides can be classified into 3 types: Ionic Hydrides, Covalent Hydrides, and Metallic or interstitial hydrides. We will have a brief look at these different types of hydrides. Considering the chemical bonds and what type of elements can react with the hydrogen atom, these hydrides can be classified into three different types. They are -
Ionic Hydrides
Covalent Hydrides
Metallic or interstitial hydrides
Each type of hydride is explained as follows.
Ionic Hydrides: The first type of classification is the ionic hydrides. Pseudohalides and saline hydrides are the other names for ionic hydrides. The ionic hydrides are formed when the alkali metals and the S block elements react with the hydrogen atoms thus forming the electrovalent compounds. These are known as the most active elements that are found in the periodic table. They tend to behave differently in the liquid state and the solid-state. The first type of classification is ionic hydrides. Saline hydrides, pseudohalides are the other names of ionic hydrides. These ionic hydrides are formed whenever the S block elements (which are known as alkaline fiesta metals) and other alkali metals react with hydrogen atoms forming electrovalent compounds. These are the most active elements in the periodic table. They behave differently in a solid-state and liquid state.
In solid-state, the ionic hydrides are non-volatile, non-conducting, and crystalline. Whereas in the liquid state, the ionic hydrides act as good conductors of electricity. Also in electrolysis, hydrogen gas is produced at the anode.
\[MH(s) + H_{2}O(l) \rightarrow MOH(aq) + H_{2}(g)(3)\]
Examples of ionic hydrides are sodium hydride (NaH), potassium hydride (KH), calcium hydride (CaH2), etc. All alkali metal hydrides come under this category.
Covalent Hydrides: The covalent hydrides are formed when 1 atom of hydrogen reacts with 1 or more nonmetal elements. The covalent bonds tend to be formed by the elements in groups 13 to 17. In comparison to the ionic hydrides, the formation of covalent hydrides is done with the electronegative elements. The sharing of the electron pairs can happen here. Another category of hydrides is covalent hydrides. These covalent hydrides are formed when one atom of hydrogen reacts with one or more nonmetal elements. Usually, the covalent bonds may be formed by elements in Groups 13 to 17. In contrast to the ionic hydrides, the covalent hydrides are formed with electronegative elements. The sharing of electron pairs can take place here. The covalent hydrides behave like both volatile and non-volatile compounds, based on the reaction.
Examples of covalent hydrides are boron hydrides, nitrogen hydrides, silicone hydride (which is saline), etc.
Metallic or Interstitial Hydrides: These are the third categories of hydrides. The metallic hydrides are nonstoichiometric and it is one of their unique qualities. Usually, the interstitial hydrides are formed by bonding between the transition elements and the hydrogen atom. These hydrides are hard in nature and have high melting as well as boiling points. These are another category of hydrides. The interstitial hydrides are nonstoichiometric. It is their unique quality. Usually, these interstitial hydrides are formed by the bonding between a hydrogen atom and transition elements. Besides being nonstoichiometric, the interstitial or metallic hydrides are very hard in nature. They have high boiling points and high melting points. All the d block and the f block elements are transition elements. They can conduct electricity but are different when compared to the ionic hydrides.
Magnesium hydride, aluminium hydride, cadmium hydride, etc. were considered as examples of these metallic hydrides.
Binary Hydrides:- Besides all these types of hydrides, binary hydrides are another special category of hydrides. Barium hydride, aluminium hydride, cesium hydride, calcium hydride, lithium hydrides, etc are examples of binary hydrides. The binary hydrides contain an element that can bond with a hydrogen atom. After the chemical bonding, the hydrogen atom acts as electronegative species. In these binary hydrides, the existence of free hydride anions is very rare.
The Uses of Hydrides
The various types of hydrides have several applications in chemistry. We list some of these applications below.
In organic chemistry, lithium aluminium hydride acts as a powerful reducing agent for chemical reactions.
Ammonia is used in various industries.
Fumigation is the chemical process where phosphine is the crucial ingredient in the process.
Metal hydrides are used in a variety of ways. They can be used for storing hydrogen, heat, and they are also used as compressors.
The hydrides are utilised as the drying agents in the textile industry.
Hydrides are also extensively used as reducing agents.
Hydride is the anion of a hydrogen atom. Hydrogen can react with other elements of the periodic table. Nucleophilic, reducing, and basic properties can be found in the chemical compounds of hydrogen, and hydride. Hydride compounds are formed with all elements of the periodic table, except a few noble gases.
Depending on the element and the bond formed with hydride ions, the properties of that particular hydride compound can be described. Its molecular formula is H- and the molecular weight is 1.008 g/mol. Also, it is observed that the hydrogen atom doesn't react with the VA group elements in the periodic table. This is nothing but a hydride gap.
FAQs on Hydride in Chemistry Complete Guide
1. What is a hydride in chemistry?
A hydride is a chemical compound in which hydrogen is bonded to another element and exists in the oxidation state −1. In hydrides, hydrogen gains one electron to form the hydride ion H- or shares electrons in covalent bonding.
- General form: E–H (where E is another element)
- Hydrogen oxidation number: −1 (except in metal hydrides with special bonding)
- Example: NaH (sodium hydride), CH4 (methane)
2. What are the types of hydrides?
Hydrides are classified into three main types: ionic (saline), covalent, and metallic hydrides. These types depend on the nature of bonding between hydrogen and the element.
- Ionic hydrides: Formed with alkali and alkaline earth metals (e.g., NaH, CaH2)
- Covalent hydrides: Formed with nonmetals (e.g., NH3, CH4)
- Metallic (interstitial) hydrides: Formed with transition metals (e.g., PdHx)
3. What is an ionic hydride?
An ionic hydride is a compound formed between hydrogen and a highly electropositive metal, containing the hydride ion H-. These are also called saline hydrides.
- Formed by Group 1 and Group 2 metals
- High melting points and crystalline solids
- Example reaction: 2Na(s) + H2(g) → 2NaH(s)
4. How do hydrides react with water?
Ionic hydrides react with water to produce a metal hydroxide and hydrogen gas. The hydride ion H- acts as a strong base and abstracts a proton from water.
- General reaction: MH + H2O → MOH + H2
- Example: NaH(s) + H2O(l) → NaOH(aq) + H2(g)
5. What is the difference between ionic and covalent hydrides?
The main difference between ionic hydrides and covalent hydrides is the type of bonding between hydrogen and the other element. Ionic hydrides contain H- ions, while covalent hydrides involve shared electron pairs.
- Ionic hydrides: Formed with metals; high melting points; react with water (e.g., NaH)
- Covalent hydrides: Formed with nonmetals; lower melting points; molecular in nature (e.g., NH3, CH4)
6. What is a metallic hydride?
A metallic hydride is a compound formed when hydrogen occupies interstitial spaces in a metal lattice. These are also called interstitial hydrides.
- Common with transition metals like Pd, Ti, and Ni
- Non-stoichiometric composition (e.g., PdHx)
- Conduct electricity and retain metallic properties
7. What is the oxidation state of hydrogen in hydrides?
The oxidation state of hydrogen in hydrides is −1. In hydrides, hydrogen gains one electron compared to its elemental state.
- In NaH, Na is +1 and H is −1
- In CaH2, Ca is +2 and each H is −1
8. How are hydrides prepared?
Hydrides are prepared by direct combination of hydrogen with elements or by chemical reduction methods. The preparation method depends on the type of hydride.
- Ionic hydrides: Direct reaction with hydrogen gas (e.g., 2Na(s) + H2(g) → 2NaH(s))
- Covalent hydrides: Formed by combination or substitution reactions (e.g., N2(g) + 3H2(g) → 2NH3(g))
- Metallic hydrides: Hydrogen absorption into metal lattice under pressure
9. Why are ionic hydrides considered strong reducing agents?
Ionic hydrides are strong reducing agents because the hydride ion H- readily donates electrons or reacts with proton sources. This makes them highly reactive in redox and acid–base reactions.
- Hydride ion is electron-rich
- Reduces water to hydrogen gas: NaH + H2O → NaOH + H2
- Used in organic and inorganic reductions
10. Can you give examples of hydrides and their formulas?
Common examples of hydrides include ionic, covalent, and metallic compounds containing hydrogen in the −1 state or bonded to another element.
- NaH – sodium hydride (ionic hydride)
- CaH2 – calcium hydride (ionic hydride)
- NH3 – ammonia (covalent hydride)
- CH4 – methane (covalent hydride)
- PdHx – palladium hydride (metallic hydride)
