Question

which of the following pieces of evidence best supports the claim that an element’s reactivity is based on its position on the periodic table?
a the noble gases are most reactive because they have the smallest radius on each period.
b the actinides are the most reactive because they are radioactive
c down any group, the reactivity decreases because the effective nuclear charge is greater.
d the halogens are the most reactive nonmetals because they have 7 valence electrons.

Explanation:

• Option A: Noble Gases are inert (not reactive) as they have a full valence shell, so this is incorrect.
• Option B: Radioactivity is not directly related to general chemical reactivity based on periodic table position, so this is incorrect.
• Option C: Down a group, for metals (e.g., alkali metals), reactivity increases because effective nuclear charge has less influence on outer electrons (shielding increases), so the statement about reactivity decreasing and reason is wrong.
• Option D: Halogens (Group 17) have 7 valence electrons, so they readily gain 1 electron to achieve a stable octet, making them the most reactive nonmetals. This relates reactivity to their position (group) and electron configuration from the periodic table.

Answer:

D. The Halogens are the most reactive nonmetals because they have 7 valence electrons.