S_N2 mechanism is followed in case of primary and secondary halides i.e., S_N2 reaction is favoured by small groups on the carbon atom attached to halogens so

CH₃ – X > R – CH₂ – X > R₂CH – X > R₃C – X

Both geometrical isomerism (cis-trans form) and optical isomerism is possible in the given compound.

No. of optical isomer = 2ⁿ = 2¹ = 2
(where n = no. of asymmetric carbon)

Hence total no. of stereoisomers = 2 + 2 = 4

Compounds which do not show optical activity inspite of the presence of chiral carbon atoms are called meso-compounds. The absence of optical activity in these compound is due to the presence of a plane of symmetry in their molecules. e.g. meso-tartaric acid is optically inactive.