Which of the following elements is NOT classified as a metalloid?

• A. B
• B. As
• C. Si
• D. Al

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the classification of elements into metals, metalloids, and nonmetals based on their physical and chemical properties.
2. Step 2: Recall that metalloids have properties intermediate between metals and nonmetals and are typically found along the 'stair-step' line on the periodic table.
3. Step 3: Identify the elements given: B (Boron), As (Arsenic), Si (Silicon), and Al (Aluminum).
4. Step 4: Recognize that B, As, and Si are located along the metalloid line and exhibit metalloid characteristics, such as semiconducting behavior.
5. Step 5: Note that Al (Aluminum) is located to the left of the metalloid line and is classified as a metal, not a metalloid.