Question

When we use sigma bond and when we use pi bond? ​

Answer 1

Answer:

Explanation:

Sigma bond represents head on collision of orbitals- as 2 orbitals can only collide head on one axis only. For eg- pₓ -- pₓ w.r.t x axis

In short sigma bond represents single bond.

while on other hand

Pi Bond represents side ways collide of orbitals- as 2 orbitals can collide in 2 side ways w.r.t  to the axis taken. For eg- pₓ -- pₓ and Py -- Py w.r.t to to y axis.

Due to this reason pi bonds are double and triple bonds.

For eg- In CO₂

there are 2 sigma (single) bonds and 2 pi (double/ triple) bonds.

Answer 2

Answer:

Sigma and pi bonds are types of covalent bonds that differ in the overlapping of atomic orbitals. Covalent bonds are formed by the overlapping of atomic orbitals. Sigma bonds are a result of the head-to-head overlapping of atomic orbitals whereas pi bonds are formed by the lateral overlap of two atomic orbitals.

The Sigma (σ) Bond

This type of covalent bond is formed by head-on positive (same phase) overlap of atomic orbitals along the internuclear axis. Sigma bonds are the strongest covalent bonds, owing to the direct overlapping of the participating orbitals. The electrons participating in a σ bond are commonly referred to as σ electrons.

Generally, all single bonds are sigma bonds. They can be formed via the following combinations of atomic orbitals.

• The overlapping of two s orbitals resulting in a sigma bond is illustrated above. This type of overlap occurs in H2 molecules, where each hydrogen atom has a half-filled s orbital.
• This type of overlapping can be observed in ammonia. An NH3 molecule features 3 sigma bonds, formed by the overlap of the 2px, 2py, and 2pz orbitals belonging to the nitrogen atom and the 1s orbitals of the three hydrogen atoms.
• A Cl2 molecule features a p-p overlap of the 3pz orbitals of two chlorine atoms. It is important to note that the head-to-head overlapping of two p orbitals gives a sigma bond whereas the lateral overlap of these orbitals leads to the formation of pi bonds.

The Pi (π) Bond

Pi bonds are formed by the sidewise positive (same phase) overlap of atomic orbitals along a direction perpendicular to the internuclear axis. During the formation of π bonds, the axes of the atomic orbitals are parallel to each other whereas the overlapping is perpendicular to the internuclear axis.