Covalent Character of Ionic Bond

As atoms of different elements, with the exception of noble gases, do not have an entire octet, they must combine with the other atoms to form a molecule bond. A covalent bond is formed when two or more atoms of the same or different elements jointly share two electrons one at a time to form a bond. An electrovalent or ionic bond, on the other hand, is created when a metal atom transmits one or even more electrons to a non-metal atom.

What are covalent bonds?

Under normal temperature and pressure conditions, covalent compounds exist as gases or liquids. A few of them are solids that are soft. Diamond, silica (SiO2),  carborundum (SiC), and other materials have an enormous three-dimensional network of structures. As a result, they have extremely high melting points. A nonpolar covalent bond formed by two similar atoms would become polar when two different substances with different electronegativities (EN) merge. Compounds with covalent bonds are not considered good electrical conductors, however when the compound is polar, it can conduct electricity in an aqueous solution. These molecules are difficult to dissolve in polar solvents such as benzene. A covalent bond is a directional and rigid bond. As a result, these compounds exhibit isomerism, or structural difference in space.

Covalent Bonding Types

Single Bond

In this case, atoms from the same or different elements hold a common electron to form covalent bonds. Examples include CH4,H2, Cl2, and so on.

Double bond

In this case, atoms of the same or distinct elements share two electrons from each other to form a double bond. Examples include C2H4,O2 CO2, and others.

Triple Bond

Each atom of the same and different elements shares three electrons in order to form three covalent bonds between the two atoms associated in the covalent bond formation. Examples include N2, C2H2, and others.

Covalent character of Ionic bond

The majority of covalent bonds have certain ionic character. Ionic bonds, too, have certain covalent character. The origin of an ionic bond’s covalent character dwells in the distortion of an electron cloud caused by an electric charge; this is known as polarizability, and the process is known as polarisation. Polarising power is the ability of an electric charge to reshape an electron cloud. The cations in an ionic compound as well as anions are developed as a result of electron loss and gain respectively. As the cations are smaller, they have greater polarising power and a higher charge density. Anions with larger sizes are easily polarised. Anion’s electrons are less strongly connected to the nucleus than cations’. The ionic bond can have a covalent character whenever the cation draws the electron cloud of the anion, causing polarisation and the electron clouds to expand out towards the cation that is present between the two ions.

As a result, the electron lost by the cation does not fully correspond to the anion, but rather returns to the cation and is shared by it.

 Fajan suggested some empirical rules for dealing with polarisation. These are known as Fajan’s rules, and they are as follows:

• The cations ought to be small in size.
• Anion of a large size.
• The presence of a cation with a high positive charge.

• Cations with electronic configuration (n-1) compared to cations with the same size and charge but ns² np⁶ (noble gas) configuration.

The covalent character of an ionic bond is enhanced by the factors listed above.

Parameters of Covalent Bonds

Each covalent bond is defined by the following parameters, which are called as covalent bond parameters:

Order of the Bond

The bond order of a molecule or ion is the number of bonds that exist between two atoms. The bond order has a fixed value. Here are some examples:

• Order of bonds = 1

If there’s only one covalent bond or sigma bond among two bonded atoms, the bond order is 1 (one). For example, H2, Cl2, and NH3.

 Single bonds are another name for these.

Three single N-H bonds present in the NH3 molecule.

• Order of bonds = 2

When there are two covalent bonds among two bonded atoms, the bond order is 2 (two).

One sigma bond and one pi bond connect the bonded atoms. These are referred to as double bonds.

• Order of Bond = 3

If there are three bonds among two bonded atoms, the bond order is 3 (three). One of these bonds is a sigma bond, and the other two are pi bonds. These are known as triple bonds.

Length of Bond

Bond length is defined as the length between the nuclei of two bonded atoms. It is measured in picometers (pm). The bond length is determined by the size of the bonded atoms and the bond order of the bond that connects them. The bond length decreases as the bond order increases.

Bonding Angle

The angle formed from two bonds in a molecule. Covalent bonds are formed by the orbitals overlapping. The angle formed by two orbitals that contain bonding electrons and overlap with other atoms’ atomic orbitals. The bond angle between two O-H bonds in an H2O molecule is 104.5°, 107.3° between N-H bonds in an NH3 molecule, and 109°28 between C-H bonds in CH4.

Conclusion 

When cations and anions come into contact, the coulombic attraction pulls anions valence shells towards the cation nucleus, causing the anion’s shape to be deformed. Polarisation is the phenomenon of an anion being deformed by a cation, and the capacity of a cation to polarise a nearby anion is referred to as cation polarising power. And the phenomenon gives rise to the covalent nature of ionic bonds.