Name: Hybridisation in SF₆ Molecule
Uploaded: 2019-07-19
Duration: 2 min 31 s
Description: Understand the bonding present in the case of sulphur hexafluoride. This video illustrates that the hybridisation present in the case of sulphur hexafluoride...

Question

Discuss with examples the directional properties of covalent bonds.

Accepted Answer

Covalent bonds are classified as sigma and pi bonds.

Sigma bond: A sigma bond is formed by the overlapping of half-filled atomic orbitals of two atoms along their internuclear axis. This type of overlapping is also called head-on overlapping or end-to-end overlapping. The sigma bond is fairly strong, as the extent of overlapping in it is maximum. Hence, $s - s, s - p$ and $p - p$ sigma bond formation is possible.

Formation of Hydrogen fluoride molecule: The electronic configuration of fluorine (Atomic No.9) is ${Is}^{2} 2 s^{2} 2 p_{x}^{2} 2 p_{y}^{2} 2 p_{z}^{1}$ . It has one half-filled 2pz atomic orbital. A hydrogen atom has one half-filled $1 s^{1}$ atomic orbital. When $1 s^{1}$ atomic orbital of hydrogen and $2 p_{z}$ orbital of fluorine overlap along their axes, a sigma bond is formed. Here, the nature of the sigma bond is $s - p$ type.

Pi $(π)$ bond: A pi $(π)$ bond is formed by the lateral or sidewise overlapping of half-filled atomic orbitals present in the valence shells of two atoms. Here, the overlapping occurs above and below the internuclear axis. The Pi bond is a weak bond, as the extent of overlapping is very small. The formation of $π$ —bond restricts free rotation between the two atoms.

Examples: (a) Formation of oxygen molecule: The electronic configuration of oxygen (Atomic No.8) ${Is}^{2} 2 s^{2} 2 p_{x}^{2} 2 p_{y}^{2} 2 p_{z}^{1}$ . Since two $p -$ orbitals are half-filled, two oxygen atoms get attached by a double bond to form an oxygen molecule.

(b) Formation of nitrogen Molecule: The electronic configuration of nitrogen (atomic number 7) is ${Is}^{2} 2 s^{2} 2 p_{x}^{1} 2 p_{y}^{1} 2 p_{z}^{1}$ . Since, here, three $p -$ orbitals are half-filled, two nitrogen atoms get attached by a triple bond to form a nitrogen molecule.

Discuss with examples the directional properties of covalent bonds.

Important Questions on Chemical Bonding and Molecular Structure

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