Draw the lewis structure for nitrogen tribromide

Step 1:
           Add valence electrons of each element present in molecule,

                         N  =  5

                        Br  =  7

                        Br  =  7

                        Br  =  7
                     ___________
Total                          26

Step 2:
           Draw Nitrogen in center surrounded by Br atoms and connect them with single bond and subtract 2 electrons/bond from total electrons. As there are three single bonds formed so subtract 6 electrons from total valence electrons.

                              26
                           -    6
                           _______
                              20

Step 3:
           Now start adding these remaining 20 electrons in pair starting from most electronegative element. So, 18 electrons are added to Br atoms and 2 electrons are added to N atom. Now, all the atoms present in the structure have there octet complete.

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.