Shape of Molecules:
The shape of covalent molecules can be determined by:
i. Electron pair repulsion theory (EPRT)
ii. Hybrid orbital theory (HOT)
Electron Pair Repulsion Theory (EPRT)
The main points of electron pair repulsion theory are:
i. There are two types of electron pairs present in covalent molecule around central atom called bond pairs and lone pairs.
ii. All electron pairs have the tendency to repel each other.
iii. The extent of repulsion between electron pairs is lone pair – lone pair > lone pair- bond pair > bond pair- bond pair.
iv. Every covalent molecule tries to attain a shape in which the repulsion between electron pair decreases.
v. According to no. of electron pairs around central atom, the shapes of covalent molecules are:
1. Tow electron pairs Linear
2. Three electron pairs Trigonal
3. Four electron pairs Tetrahedral
Hybrid Orbital Theory (HOT)
According to Hybrid orbital theory, the shape of covalent molecule depends upon hybridization of central atomic.
i. If central atom undergoes Sp hybridization, shape of molecule is Linear with 180° angle.
ii. If central atom undergoes Sp² hybridization, shape of molecule is Trigonal with 120° angle.
iii, It central atom undergoes Sp³ hybridization with no lone pair, shape of molecule is Tetrahedral with 109.28″ angle.
iv. If central atom undergoes Sp3 hybridization with one lone pair, shape of molecule is Tetrahedral with 107° angle.
v. lf central atom undergoes Spa hybridization with two lone pair, shape of molecule is Tetrahedral with 104° angle.