Which of the following is NOT considered a greenhouse gas?

The correct answer is nitrogen, as it is not considered a greenhouse gas. Greenhouse gases are substances in the atmosphere that can absorb and emit infrared radiation, contributing to the greenhouse effect, which leads to the warming of the Earth's surface. Carbon dioxide, methane, and water vapor are all well-known greenhouse gases that trap heat in the atmosphere and play significant roles in climate change.

Nitrogen, on the other hand, makes up a large portion of the Earth's atmosphere but does not have the properties necessary to absorb infrared radiation. Instead, nitrogen is considered a stable and inert gas that does not interact significantly with thermal energy, which is why it is not classified as a greenhouse gas. Understanding the differences in these gases is essential for grasping the mechanisms behind climate change and the role that various substances play in our atmosphere.