As you move down Group 1 of the periodic table, which of the following trends is observed?

• A. The elements become less reactive.
• B. The ionization energy increases.
• C. The electronegativity increases.
• D. The atomic radius increases.

Answer: (D)

Verified step by step guidance

1. Identify the group in question: Group 1 of the periodic table, also known as the alkali metals.
2. Recall the general trend for atomic radius in a group: As you move down a group, new electron shells are added, increasing the distance between the nucleus and the outermost electrons.
3. Understand how this affects atomic radius: More electron shells mean a larger atomic radius because the outer electrons are farther from the nucleus.
4. Consider other properties mentioned (reactivity, ionization energy, electronegativity) and how they change down the group: Reactivity actually increases, ionization energy decreases, and electronegativity decreases as you move down Group 1.
5. Conclude that the correct trend observed down Group 1 is that the atomic radius increases due to the addition of electron shells and increased distance of valence electrons from the nucleus.