Covalent Bond | Definition, Structure & Properties

Covalent bonding, also called atomic bonding, is a chemical bond that shares electron pairs between atoms. These electron pairs are called shared pairs or bond pairs, and the constant equilibrium of attractive and repulsive forces between atoms, when they share electrons, is called covalent bonding.

Covalent Bonds

For many molecules, the sharing of electrons allows each atom to receive the equivalent of a complete outer shell in accordance with the stable electronic configuration. Inorganic chemistry, covalent bonds are more common than ionic bonds.

Covalent bond hydrogen

The covalent bond includes many kinds of bonds like π-bond, metal-to-metal bond, nonlinear interactions, bent bonds, and three-center two-electron bonds. The term covalent bond dates back to 1939. The prefix co-means jointly, in action, to a lesser degree, sharing, etc. Thus the “covalent bond”, in essence, shares the “valence” discussed in the valence bond theory.

In the H2 molecule, hydrogen atoms share two electrons through covalent bonding. The covariance between molecules of similar electronegativity is great. Therefore, the covalent bond does not need to have two atoms with the same elements, only comparable electronegativity. The covalent bond involving electrons on more than two atoms is known to be delocalized.

Types of covalent bonds

Nuclear orbits (excluding s orbits) have specific directional properties, leading to a variety of covalent bonds. Sigma (σ) bonds are strong covalent bonds that result from overlapping orbits on two different molecules. A single bond is usually a σ (sigma) bond. The Pi (π) bonds are weak and are due to lateral overlap between the P or D orbital. The double bond between two given atoms is one σ and one π bond, and the triple bond is one σ and two π bonds.

Covalent bonds are also affected by the electronegativity of the bonded molecules, which determines the chemical polarity of the bond. Two molecules with equal electronegativity form nonpolar covalent bonds, such as H-H. The asymmetric relationship creates a polar covalent bond such as H – Cl. However, geometric asymmetry is required for polarity; otherwise the dipole can be dissolved as a result of a non-polar molecule.

 

Covalent bond structures

There are many types of structures for covalent substances, including individual molecules, molecular structures, macro electric structures, and large covalent structures. Individual molecules have strong bonds that hold atoms together, but there are negligible forces of attraction between atoms. Such covalent substances are usually in gaseous form, for example, SO2, CO2, HCl, and CH4. In molecular structures, weak forces of attraction are present. Such covalent substances are low-boiling-temperature liquids (like ethanol) and low-melting-temperature solids (like iodine and solid CO2). Macromolecular structures link large numbers of molecules with covalent bonds in chains, including synthetic polymers such as polyethylene and nylon, and biopolymers such as proteins and starch. Network covalent structures (or large covalent structures) contain large numbers of molecules connected in sheets (like graphite) or 3-dimensional structures (such as diamond and quartz). These materials have high melting and boiling points, are often fragile, and have high electrical resistance. Elements with high electronegativity and the ability to form three or four electron pair bonds often form such large bulk cell structures.

Covalent bond structures

One- and three-electron bonds

Bonds with one or three electrons can be found in radical species, which contain an odd number of electrons. A simple example of the 1-electron bond is found in the dihydrogen cation, H2+. One-electron bonds often have half the bond energy of a 2-electron bond and are therefore called “half bonds”. However, there are exceptions: in the case of dilithium, the bond to 1-electron Li2+ is actually stronger than the 2-electron Li2. This exclusion can be explained in terms of hybridization and inner-shell effects.

The simplest example of a three-electron bond can be found in the helium dimer cation, He+2. It is considered “half bond” because it contains a shared electron (rather than two); In terms of atomic orbit, the third electron is in an anti-bonding orbit, which dissolves half of the bond that is formed by the other two electrons. Another example of a molecule having a 3-electron bond is the addition of two 2-electron bonds, nitric oxide, NO. The oxygen atom, O2, can also be considered to have two 3-electron bonds and a 2-electron bond, which causes its paramagnetism and its formal bond to 2. Chlorine dioxide and its heavy analogs, bromine dioxide and iodine dioxide, also have three-electron bonds.

Molecules with odd-electron bonds are usually highly reactive. This type of bond is only stable between atoms with similar electronegativity.

covalent bond examples

Nitric oxide

Nitric oxide

Di oxygen

covalent bonds Di oxygen

 

Covalent Bond Properties

A few physical properties of particles/mixes are identified with the nearness of covalent bonds:

  • Covalent bonds between iotas are very solid, yet attractions between particles/mixes, or intermolecular powers, can be moderately frail. Covalent mixes by and large have low bubbling and liquefying focuses, and are found in every one of the three physical states at room temperature.
  • Covalent mixes don’t lead power; this is on the grounds that covalent mixes don’t have charged particles equipped for moving electrons.
  • Lewis hypothesis likewise represents bond length; the more grounded the bond and the more electrons shared, the shorter the bond length is.