What is one of the characteristics of chlorine gas?

Chlorine gas is notably characterized by its greenish-yellow color, making it identifiable and distinct in its appearance. This characteristic is important for safety and handling because the color alerts individuals to its presence, which is critical in environments where chlorine is used, such as water treatment facilities.

In contrast, the other options present attributes that do not accurately describe chlorine gas. For instance, chlorine is not odorless; it has a strong, pungent smell, which adds to its identification as a hazardous gas. Additionally, while chlorine gas is heavier than air, it is not classified as non-corrosive; in fact, chlorine can be quite corrosive, reacting with many materials, which is essential for operators to recognize to ensure proper handling and safety measures in operations involving this chemical.