According to Markovnikov's rule ," the incoming electrophile will bond to that carbon which has greater number of hydrogen atom or less number of carbon atoms". Hence in case of 1-Heptene the electrophile (Hydrogen) goes to carbon one because it has two hydrogen atoms as compare to carbon two, containing only one hydrogen.
Result:
The major product formed in this reaction is 2-Bromoheptane. Reaction is shown below,