How does halogen reactivity change as you move down Group 7?

How does halogen reactivity change as you move down Group 7?

• A. Stays the same
• B. Random
• C. Increases down the group
• D. Decreases down the group

Answer: (D)

Halogens react by gaining one electron to form halide ions, so how reactive they are depends on how easily they attract an extra electron. As you move down Group 7, the atoms get larger and there’s more shielding of the outer electrons from the nucleus, so the outer electrons feel less pull from the nucleus. This weaker attraction makes it harder for the halogen to attract and accept an extra electron, so reactivity decreases. Fluorine, being the smallest, pulls electrons in strongly and is the most reactive, while iodine, with its larger size, is much less reactive. In practical terms, the oxidising power of halogens falls down the group.

Halogens react by gaining one electron to form halide ions, so how reactive they are depends on how easily they attract an extra electron. As you move down Group 7, the atoms get larger and there’s more shielding of the outer electrons from the nucleus, so the outer electrons feel less pull from the nucleus. This weaker attraction makes it harder for the halogen to attract and accept an extra electron, so reactivity decreases. Fluorine, being the smallest, pulls electrons in strongly and is the most reactive, while iodine, with its larger size, is much less reactive. In practical terms, the oxidising power of halogens falls down the group.