optical isomer of an alkane

heptane
2methyl hexane
3 methyl hexane
2,2 dimenthyl pentane
2,3 dimethyl pentane
2,4 dimentyl pentane
3,3 dimentyl pentane
3 ethyl pentane
2,2,3 trimethyl butane

did i miss somethign?

I think two optical isomers are possible
3-methylhexane and its mirror image

kumar is right as 3-methylhexane has a chiral carbon atom
but there one more possibility
2,3-dimethylpentane and its mirror image
so there are 4 otical isomers of C₇H₁₆