Which of the following statements best describes the relationship between the position of nonmetals on the periodic table and their chemical reactivity?

Nonmetals become more reactive as you move from left to right across a period because their electronegativity increases and they need fewer electrons to complete their valence shell, so they readily gain or share electrons. Down a group, their reactivity drops because the valence electrons are farther from the nucleus and are shielded by inner shells, making it harder to attract or share electrons. Thus, a nonmetal in a higher period of the same group is less reactive than one in a lower period. For example, chlorine in period 3 is more reactive than iodine in period 5, even though both are halogens, because chlorine’s valence electrons are closer to the nucleus and more easily attracted.