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All those elements whose ionization energy is very high are unable to transfer electrons and those elements whose electron affinity is very low are unable to take electrons. Atoms of such elements share their electrons with atoms of other elements or with other atoms of the same element in such a way that both the atoms attain octet configuration in their valence shells and achieve stability. The pairs of electrons participating in a covalent bond are called bonding pairs or shared pairs. This bonding by sharing of different or same type of electron pairs is known as covalent bonding.
types of covalent bonds
Covalent bonds can be classified into 5 categories:
- single covalent bond
- double covalent bond
- triple covalent bond
- polar covalent bond
- nonpolar covalent bond
Click to Check – Periodic Table: Groups, Properties, And Laws
- single covalent bond
Single covalent bonds are formed when only one pair of electrons is shared between the two participating atoms. This form of covalent bond has a lower density and is weaker than double and triple bonds but is the most stable bond.
Example: The HCl molecule has one valence electron with one hydrogen atom and seven valence electrons with one chlorine atom. A single bond is formed between hydrogen and chlorine by sharing one electron in their valence shell.
- double covalent bond
A double covalent bond is formed when two pairs of electrons are shared between two participating atoms. Double covalent bonds are stronger than single bonds, but they are less stable.
Example: In the formation of the oxygen molecule, each oxygen atom has six electrons in its valence shell. Each atom needs two more electrons to complete its octet. So the atoms each share two electrons to form an oxygen molecule. Since two electron pairs are shared there is a double bond between the two oxygen atoms.
- triple covalent bond
A triple bond is formed when three pairs of electrons are shared between two participating atoms. Triple covalent bonds are represented by three dashes (≡) and are the least stable type of covalent bond.
Example: In the formation of the nitrogen molecule, each nitrogen atom that has five valence electrons donates three electrons to form three electron pairs to share.
- polar covalent bond
This type of covalent bond exists where there is unequal sharing of electrons due to difference in electronegativity of the combining atoms. More electronegative atoms will have a greater pull for electrons. The electronegativity difference between atoms is greater than zero and less than 2.0. As a result, the shared pair of electrons will be closer to that atom.
Example: Molecules forming hydrogen bonds as a result of unbalanced electrostatic potential. In this case, the hydrogen atom interacts with electronegative fluorine, hydrogen or oxygen.
- nonpolar covalent bond
This type of covalent bond is formed when there is an equal share of electrons between atoms. The difference in electronegativity between two atoms is zero. Non-polar covalent bonds occur where the combining atoms have the same electron affinity (diatomic elements).
Example: Nonpolar covalent bonding is found in gas molecules like hydrogen gas, nitrogen gas, etc.
Properties of covalent bonds
Some properties of covalent bonds are given below:
- Covalent bonds are very strong chemical bonds that exist between atoms.
- Covalent bonds do not create new electrons. The bond only connects them.
- Covalent bonds rarely break on their own after being formed.
- Covalent bonds are directional where the bonded atoms exhibit specific orientations relative to each other.
- Most compounds containing covalent bonds have relatively low melting and boiling points.
- Compounds containing covalent bonds generally have low enthalpies of vaporization and fusion.
- Covalent compounds do not conduct electricity due to lack of free electrons.
Covalent compounds are not soluble in water.
Difference Between Covalent and Ionic Bonds
Candidates can see the comparison between covalent bond and ionic bond.
| Covalent Bonds | Ionic Bonds |
| A covalent bond is formed between two similar electronegative non-metals | This type of bond is formed between a metal and a non-metal |
| Bonds formed from covalent bonding have a Definite shape | Ionic Bonds have No definite shapes |
| Covalent bonds have low Melting Point and Boiling Point | Ionic Bonds have High Melting Points and Boiling Points |
| Covalent bonds have Low Polarity and more Flammable | Ionic Bonds have High Polarity and are less Flammable |
| Covalent Bonds are in a Liquid or gaseous State at room temperature | At room temperature, Ionic Bonds are in Solid-state. |
| Examples: Methane, Hydrochloric acid | Example: Sodium chloride, Sulfuric Acid |
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