Why does the lightest halogen, which is also the most chemically reactive, exhibit a decrease in reactivity as you move down the column of halogens in the periodic table? Explain this trend in terms of periodic properties.

Verified step by step guidance

1. Identify the lightest halogen: The lightest halogen is fluorine, which is located at the top of Group 17 (the halogens) in the periodic table.
2. Understand the concept of reactivity: Reactivity in halogens is largely determined by their ability to gain an electron to achieve a stable noble gas electron configuration.
3. Discuss atomic size and electron affinity: As you move down the group from fluorine to iodine, the atomic size increases. This is because additional electron shells are added, increasing the distance between the nucleus and the valence electrons.
4. Explain the effect of increased atomic size: With a larger atomic size, the attraction between the nucleus and the incoming electron decreases, making it harder for the atom to gain an electron and thus decreasing reactivity.
5. Summarize the trend: Therefore, the reactivity of halogens decreases as you move down the group due to the increase in atomic size and the corresponding decrease in electron affinity.