Consider four elements from group 7a: fluorine in the second period, chlorine in the third period, bromine in the fourth period, and iodine in the fifth period. which element has the largest first ionization energy?

Fluorine

This is because the atom of the fluorine is the smallest, meaning its electrons have the least amount of shielding effect and are held together tightly. As we progress down the group, another shell of electrons is added each time, increasing the shielding effect and making electron removal easier.

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.