Which of the following elements, most abundant in Earth's crust, is classified as a nonmetal?

• A. Aluminum
• B. Oxygen
• C. Calcium
• D. Iron

Answer: (B)

Verified step by step guidance

1. Identify the elements listed: Aluminum, Oxygen, Calcium, and Iron.
2. Recall the classification of elements into metals, nonmetals, and metalloids based on their properties.
3. Recognize that Aluminum, Calcium, and Iron are metals, characterized by their conductivity, malleability, and metallic luster.
4. Understand that Oxygen is a nonmetal, which typically has poor electrical conductivity and exists as a gas at room temperature.
5. Conclude that among the most abundant elements in Earth's crust listed, Oxygen is the nonmetal.