Provide information about the structure and isomerism of alkenes.

(N/A) Alkenes are unsaturated hydrocarbons containing at least one carbon-carbon double bond $(C=C)$. The general formula is $C_nH_{2n}$.
$1$. Isomerism in Alkenes:
Alkenes with $4$ or more carbon atoms exhibit structural isomerism.
$(a)$ Position Isomerism:
This arises due to the different positions of the double bond in the carbon chain. For example,butene $(C_4H_8)$ shows position isomerism:
$(I)$ $CH_2=CH-CH_2-CH_3$ (But-$1$-ene)
$(II)$ $CH_3-CH=CH-CH_3$ (But-$2$-ene)
$(b)$ Chain Isomerism:
This arises due to the difference in the structure of the carbon chain. For example,butene $(C_4H_8)$ and $2$-methylprop-$1$-ene $(C_4H_8)$ are chain isomers:
$(I)$ $CH_2=CH-CH_2-CH_3$ (But-$1$-ene)
$(III)$ $CH_2=C(CH_3)-CH_3$ ($2$-Methylprop-$1$-ene)
Chain isomers possess the same molecular formula but different carbon skeletons.