The article tells all about Chemical Bonding, its Causes and types of Chemical bonding.
A chemical bond is a force that acts between two or more atoms to hold them together as a stable molecule. The number of chemical bonds formed by an atom in a molecule is termed as Valency.
Causes of Chemical Combination/Bonding-
- Tendency to acquire Noble Gas Configuration- all the atoms have urge to attain a stable state configuration of eight electron in their valence shell. This principle of attaining maximum of eight electron in the valence shell is called Octet Rule.
- Tendency to acquire Minimum Energy- Every object in Universe loose energy to attain a stable state. Atoms have high potential energy. An atom combines with other atoms to form molecules. It loses some amount of potential energy to attain a stable state.
- An atom that loses one or more electrons is known as Electropositive Elements.
- An atom that gains one or more electrons is called as Electronegative Elements
- An atom which has little tendency to lose or gain electrons is known as Noble Elements.
Types of Bonding- Based upon the force of attraction to hold the atoms together, there are three types of bondings: –
- Ionic Bond- it involves complete transfer of one or more electron from one atom to another. This type of bond is formed between the electropositive and electronegative elements. The two atoms have electrostatic force of attraction which holds the oppositely charged ions together.
The compounds which have ionic or electrovalent bonds are called Ionic or Electrovalent Compounds e.g. CaF2, NaCl etc.
Properties of Ionic Bond-
- Exist in crystalline solid
- Have high melting points and boiling points
- Generally soluble in water
- Good conductor of electricity in molten or liquid state
- They split up into oppositely ions when dissolved in water.
2. Covalent Bonds- this bond is formed by mutual sharing of electrons between combining atoms. When two electronegative atoms react together, both atoms have tendency to gain electron. In such a case atom share electron so as to attain noble gas configuration.
A covalent bonding is formed by sharing of one, two or three electron pair which form correspondingly single, double and triple covalent bonds.
Properties of Covalent Bond-
- It does not exist as ions but exists as molecules.
- Melting point and boiling point are generally low.
- Generally insoluble or less soluble in water
- Non-conductors of electricity.
3. Metallic Bond- metals are made up of positive ions packed together. The negatively charged electrons hold the ion together. The number of positive and negative charge is exactly balanced.
Properties of Metallic Bond-
- High electrical and thermal conductivity due to mobility of electrons
- Malleable and ductile
- Crystals are cubic close-packed, hexagonal close-packed, or body centred cubic.
- Forms alloys readily.
Important theories of chemical bonding-
- Valence Shell Electron Pair Repulsion Theory-
- Molecular Orbital theory
Characteristics of Bonds-
- Average distance between the centre of nuclei of two bonded atoms in molecules.
- Average angle with the central atom of molecules e.g. H-O-H has 109.5 degree.
- Single bond of a molecule requires less energy of disassociation than the double or triple bond of same molecule.
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