Final answer:
Chlorine (Cl), option D, is the nonmetal among the choices listed. It belongs to the halogen group, which consists of nonmetals known for forming compounds with metals.
Step-by-step explanation:
To determine which of the following is a nonmetal, we should look at their placement in the periodic table and their properties:
- Potassium (K) is in group 1, known as the alkali metals.
- Aluminum (Al) is a post-transition metal.
- Calcium (Ca) is in group 2, known as the alkaline earth metals.
- Chlorine (Cl) is in group 17, known as the halogens, which are nonmetals.
Therefore, the answer is D. Chlorine (Cl), which is a nonmetal and part of the halogen group. Halogens are known for readily reacting with metals to form various compounds, including salts.