These MP Board Class 11th Chemistry Notes for Chapter 4 Chemical Bonding and Molecular Structure help students to get a brief overview of all the concepts.

## MP Board Class 11th Chemistry Notes Chapter 4 Chemical Bonding and Molecular Structure

→ Chemical bond : Electrons of outermost shell participate in combination.

→ Lewis structure : Representation of electrons of outermost shell by dots. Lewis symbol is an easy way of representation of valence electrons.

→ s-orbital is spherical, p-orbitals are of three types : px, py and pz. Their shape is like dumbbell.

→ d-orbitals are situated on two axis, are double dumbbell in shape and are of five types : dxy,dyz, dxz,dx2 – y2, dz2

→ Valence bond theory was proposed by Linus Pauling.

→ Molecular orbital theory was proposed by Robert Mullican.

→ Bond order = $$\frac { 1 }{ 2 }$$ (Nb – Na).

→ Higher the bond order, higher is the dissociation energy.

→ Paramagnetic molecule: If unpaired electrons are present in a molecule, then the molecule is paramagnetic.

→ Molecular orbital: These are formed by the combination of atomic orbitals.

→ Atomic orbitals are of three types :

• Bonding molecular orbital : Their energy is minimum, lesser than the energy of the component atomic orbitals.
• Non-bonding molecular orbital: Molecular orbitals whose energy is equal to the energy of the component atomic orbitals.
• Antibonding molecular orbital: These are the molecular orbitals, whose energy is maximum and is higher than the energy of the component atomic orbitals.

→ In molecular orbitals, electrons are filled in the increasing order of their energy.

→ With the increase in bond order, bond length decreases.

→ Ionic or Electrovalent bond: Electrostatic attraction between cation formed by loss of electrons and anioi formed by the gain of electrons.

→ Chemical bond : Sharing of equal numbers of electrons between the two combining atoms.

→ Co-ordinate bond : Donation of an electron pair from one atom to another atom. It contains both ionic and polar character.

→ Orbital theory oi covalent bond : Formation of covalent bond between two atoms is due to overlapping of orbitals with unpaired electrons.

→ VSEPR theory : Any molecule orient in such a way that there should be maximum distance between electron pairs of valence shell and minimum repulsion. Order of repulsion between bond pair and lone pair is following :
bond pair – bond pair < lone pair – bond pair < lone pair – lone pair

→ Quantum theory of covalent bond : By overlapping of orbitals or bonding electrons 5-bonds and p-bonds are formed; 5-bonds are stronger than p-bonds.

→ a-bond: Bond formed between axial overlapping of atomic orbitals (s -s, s-p and p-p). a-bond can exist alone.

→ 7t-bond : Bond formed between lateral overlapping of (p-p) atomic orbitals, jr-bonds are formed only when 5-bonds are formed or existing.

→ Hybridization: Atomic orbitals of similar energies mixed and same number of orbitals of same energy and shape are formed. This process is called hybridization.

→ Hydrogen bond : The electrostatic force which exist between H-atom of one molecule with highly electro-negative element of the other molecule is called Hydrogen bond.

→ Intra-molecular hydrogen bond: When hydrogen atom and electro-negative element both are present in the same molecule, then this type of hydrogen bond formed is called intra molecular hydrogen bond.

→ Inter-molecular hydrogen bond: When hydrogen atom and electro-negative element are present in different molecules, this type of H-bond formed is called inter-molecular hydrogen bond.

→ Resonance: To explain the characteristic properties of molecules, more than one structures are required and the actual structure is supposed as resonance hybrid of these structures.

→ Dipole moment is represented by an arrow pointing towards the more electro-negative element.