Hydrogen is the simplest element of periodic table having a single proton and a single electron. The single electron is situated in the 1s shell, which can hold two electrons. The electronic configuration of hydrogen is thus not stable. In order to fill up the 1s shell, two hydrogen atoms join and share the second electron. This is identified as covalent bonding and in this case the formation of a hydrogen molecule takes place.

The hydrogen molecule (H2) is the simplest matter having a covalent bond. It forms as of two hydrogen atoms, every with one electron in a 1s orbital. Both hydrogen atoms in H2 molecule share their one electron in the covalent bond, and each acquires a helium-like electron configuration.

Only hydrogen atom and the halogen atoms form one covalent bond to other atoms in mainly stable neutral compounds. On the other hand, the carbon, oxygen, and nitrogen atoms can simultaneously bond to more than one atom.

The bond joining two hydrogen atoms in a hydrogen molecule (H2) is a usually covalent bond. The bond is easy to examine for the reason that the hydrogen atoms only have one proton and one electron both atoms. Since the hydrogen atoms are alike, neither can take the electron from the other to complete its electronic shell to fulfill duplet rule of electrons and form an ionic bond. As a result, the two hydrogen atoms just have only choice to share the two electrons in a covalent bond. The electrons pay out most of their time among the positively charged hydrogen nuclei, attracting themselves both to the negative charge of the two electrons.

Covalent Bonds in Hydrogen Molecule:

A covalent bond consists of the immediate forces of attractions of two nuclei for one or more pairs of electrons. The electrons to be found between the two nuclei are bonding electrons. Covalent bonds occur between the same atoms or between different atoms whose variation in electronegativity is insufficient to permit transfer of electrons to form ions.

Let’s regard as the covalent bond in the hydrogen molecule (H2). A hydrogen molecule forms from two hydrogen atoms every atom has one electron in a 1s orbital. The two hydrogen atoms are attracted to the equal pair of electrons in the covalent bond. The bond is shown either as a pair of “dots” or else as a solid line. Each hydrogen atom attains a helium-like electron configuration. The atomic nuclei are estranged via an equilibrium distance logically known as bond length.

Energy can be release out when the electrons combine with the two hydrogen atoms form a covalent bond. Bond configuration releases heat; as a result, it is exothermic reaction. The heat released while one molecule of a compound forms at 298K is the standard enthalpy change (ΔH°) for the procedure. ΔH° for formation of a mole of hydrogen molecule from two hydrogen atoms is − 435 kJ mole− 1. Since energy is released in the reaction, the hydrogen molecule is extra stable than two isolated hydrogen atoms. The reverse procedure, breaking the H—H bond, requires 435 kJ mole− 1, extent called the bond strength.

The number of covalent bonds an atom can form is known as valences of that atom. In a single covalent bond, when the electrons are shared among two s orbitals, the resultant bond is a sigma (σ) bond .Sigma bonds are the most stable covalent chemical bonds. Sigma bonds also occur when an s and a p orbital share a pair of electrons or when two p orbitals that are equivalent to the internuclear axis share a pair of electrons. For example, both of the hydrogen atoms in water (H2O) is bonded to the oxygen using a single bond (σ bond)