Why bond forms?• In atomic states atoms are unstable and they possess high potential energy.

• Atoms want to stable and lower their potential energy.

Therefore, bond is formed.

What is Chemical Bond?A chemical bond is an attraction between atoms that allows the formation of chemical substances which contain two or more atoms.

Importance of chemical bonding

• To understand the physical properties of substances such as, density, m.p, b.p, luster.

• To understand the chemical properties of the species like, reactivity, pH, chemical potential.

• To differentiate between ionic, covalent and metallic substances.

• Chemical bonding brings new substances to us i.e. it brings diversity to our life.

• New technology and industries are largely depend on the assumption of bonding.

Octate ruleIt states that atoms tend to combine in such a way that they have eight electrons in their valence, giving them the same electronic configuration as a noble gas.

The bonding in carbon dioxide (CO2): all atoms are surrounded by 8 electrons, fulfilling the octet rule

Octate rule

8 Valence electrons

Octate rule

8 Valence electrons

Octate rule

8 Valence electrons

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electronsC would

like to N would like toO would like to

Gain 4 electronsGain 3 electronsGain 2 electrons

Types of Chemical bonds

According to formation of bonds:

1. Ionic bonds 2. Covalent bonds 3. Metallic bonds4. Co-ordinate covalent bonds

IONIC BONDIonic bond is formed between two ions by the

transfer of electrons

Ionic Bond• Between atoms of metals and nonmetals with very different electronegativity

• Bond formed by transfer of electrons.

• Produce charged ions all states. Conductors and have high melting point.

• Examples; NaCl, CaCl2, KCl

Sodium Ion formation Sodium atom Sodium ion

Na – e Na +

2-8-1 2-8 ( = Ne)

Chloride Ion formation unpaired electron octet

1 - : Cl + e : Cl :

2-8-7 2-8-8 (= Ar)

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

COVALENT BONDCovalent bond is formed by the

sharing of electrons.

Covalent Bond• Between nonmetallic elements of similar electronegativity.

• Formed by sharing electron pairs

• Stable non-ionizing particles, they are not conductors at any state

• Examples; O2, CO2, C2H6, H2O and so on.

Two nonmetal atoms form a covalent bond because they have less energy after they bonded

H +

H H : H or HH or H2

hydrogen molecule

Single Covalent Bond

single bond

Double Covalent Bond

2 pairs of electrons are shared between 2 atoms

Example O2

O +

O O::O or O=O or

double bond

O2

Triple Covalent Bond3 pairs of electrons are shared

between 2 atoms

Example N2

N +

N N:::N or N N or N

triple bond

2