Write down structural formulas and name isomeric compounds (3 isomers).

In simple terms, isomers are the same composition (the same number of atoms in a molecule), but a different structure. There are structural isomers and interclass
Example:
(butene – 1 (starting alkenes)
CH3 – CH2 – CH = CH2

(butene – 2 (changed the structure by changing the position of the multiple (double) bond, but the composition is the same – the structural isomer)
CH3 – CH = CH – CH3

(2 – methylpropene – 1 (the structure was changed, the carbon chain became shorter, but a methyl radical appeared, and the composition was the same – the structural isomer))

CH3 – C = CH2
I
CH3

(cyclobutane (changed the class of the compound (became cycloalkane), but the composition is the same – the interclass isomer)

CH2 – CH2
I I
CH2 – CH2