Dear Student,
Heptane is a saturated 7 C compound , having chain isomers.
The isomers are
CH3-CH2-CH2-CH2-CH2-CH2-CH3 n-heptane
CH3-CH(CH)3-CH2-CH2-CH2-CH3 2-methyl hexane
Similarly you can make structures for 3-methyl and 4-methyl heptane.
CH3-C(CH3)2- CH2-CH2-CH3 2,2 -dimethyl pentane
similalry you can make structures for 3,3 -demethyl and 4,4- dimethyl
The other isomers will be 2,3 -dimethyl heptane and
3,4 dimethyl heptane
2,4 dimethyl hepatne
Regards!