Molecules of 1-bromopropane and 2-bromopropane differ in
(1) molecular formula(2) structural formula(3) number of carbon atoms per molecule(4) number of bromine atoms per molecule

(2) structural formula

Explanation:-

The compounds having similar molecular formula but different arrangement of atoms or groups in space are called isomers and the phenomenon is called as isomerism.  

1-bromopropane and 2-bromopropane are position isomers which have same molecular formula but different position of the functional groups attached.

The chemical formula for both the compounds 1-bromopropane and 2-bromopropane is . Thus both have same molecular formula , 3 carbon atoms per molecule and 1 bromine atom per molecule.

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