Covalent Bonding

Covalent Bonding

  1. Covalent bonds are formed by atoms sharing electrons to form molecules. This type of bond usually formed between two non-metallic elements.
  2. In the formation of covalent bonds, atoms of non-metals will combine with each other to donate one, two or three electrons for sharing.
  3. The compound formed through the formation of covalent bonds is called the covalent compounds.

Examples of Covalent Compound

Covalent Compound FormulaCovalent Compound Formula
ChlorineCl2PhosphorusP4
HydrogenH2Sulfur dioxideSO2
OxygenO2Carbon dioxideCO2
NitrogenN2Tetrachloro-methaneCCl4

Examples of Formation of Covalent Compounds

Formation of Fluorine Molecule

  1. The electrons arrangement of a fluorine atom is 2.7
  2. To achieve octet electrons arrangement, 2 fluorine atoms share 1 pair of electrons between each other.
  3. As a result, a covalent bond formed between the 2 atoms.
Formation of Oxygen Molecule
  1. The electrons arrangement of an oxygen atom is 2.6
  2. To achieve octet electrons arrangement, 2 fluorine atoms share 2 pair of electrons between each other.
  3. As a result, 2 covalent bonds formed between the 2 atoms.

Formation of Carbon Dioxide Molecule

  1. The electrons arrangement of an oxygen atom is 2.6 and the electrons arrangement of a hydrogen atom is 1.
  2. To achieve octet electrons arrangement, the oxygen atom share 2 pair of electrons with 2 hydrogen atoms.
  3. The hydrogen atoms achieve duplet electrons arrangement after sharing electron with the oxygen atom.
  4. As a result, covalent bonds formed between the oxygen atom and the hydrogen atoms.

Number of Bond

Number of Bond

  1. There are 3 types of covalent bond:
    1. Single covalent bond – sharing of one pair of electrons
    2. Double covalent bond – sharing of two pairs of electrons
    3. Triple covalent bond – sharing of three pairs of electrons

Example

Number of electronExample and type of covalent bond
1 pair

type of covalent bond: Single Bond

2 pair

type of covalent bond: Double Bond

3 pair

type of covalent bond: Triple Bond

Formation of Single Bond (Hydrogen Molecule)

Formation of Double Bond (Oxygen Molecule)

Formation of Triple Bond (Nitrogen Molecule)

Predicting the Molecular Formula of Covalent Compounds

  1. Like the formula of ionic compounds, the formula of most covalent compounds can be predicted by referring to the group in periodic table of the elements in the compound.
  2. We can predict the formula of a covalent compound by referring to the valency of the elements in the compound, if we know which group in periodic table the element is located.
  3. The valency of an atom is the number of electrons receive of release to achieve octet electrons arrangement.
  4. For example, the electron arrangement of an oxygen atom is 2.6. To achieve octet electrons arrangement, the oxygen atom need to receive 2 electrons. Therefore, the valency of oxygen is 2.
  5. Table below shows the group of the elements, the valency of the elements and the predicted formula of covalent compounds formed among the elements.

Element that combine Formula of the covalent compound
Element X from Valency Element Y from Valency
Group 15
3
Group 15
3
 XY
Group 15
3
Group 16
2
 X2Y3
Group 15
3
Group 17
1
 XY3
Group 16
2
Group 16
2
 XY
Group 16
2
Group 17
1
 XY2
Group 17
1
Group 17
1
 XY