Which group III element is expected to have physical and chemical properties that are least similar to the other elements in that family?

• (A) B
• (B) Al
• (C) Ga
• (D) Tl

The group III elements in the periodic table include boron (B), aluminum (Al), gallium (Ga), and thallium (Tl). Among these, boron is expected to have physical and chemical properties that are least similar to the others.

Reasons for Boron's Unique Properties

• Non-metallic Nature: Boron is a metalloid, while aluminum, gallium, and thallium are metals.
• Bonding Characteristics: Boron tends to form covalent bonds, whereas the other three elements typically form metallic bonds.
• Reactivity: Boron reacts differently with acids and bases compared to the more metallic behavior of Al, Ga, and Tl.

Thus, the answer is (A) B, as boron stands out in terms of its distinct properties within group III elements.