Explain geometric isomerism with an example.

(N/A) Geometric isomerism arises due to the restricted rotation around the carbon-carbon double bond $(C=C)$. Because the $\pi$ bond prevents free rotation,atoms or groups attached to the doubly bonded carbons are fixed in space,leading to different spatial arrangements.
$1$. $Cis$-isomer: When identical atoms or groups are on the same side of the double bond,it is called a $cis$-isomer.
$2$. $Trans$-isomer: When identical atoms or groups are on opposite sides of the double bond,it is called a $trans$-isomer.
Example: $But-2-ene$ $(CH_3-CH=CH-CH_3)$
In $cis-but-2-ene$,both $CH_3$ groups are on the same side of the $C=C$ bond.
In $trans-but-2-ene$,the $CH_3$ groups are on opposite sides of the $C=C$ bond.
These isomers cannot be interconverted without breaking the $\pi$ bond,making them distinct chemical species.