What gas makes up the majority of the atmosphere?

The majority of the Earth's atmosphere is composed of nitrogen, which accounts for about 78% of the total atmosphere by volume. Nitrogen is a diatomic molecule (N2) and is largely inert, meaning it does not readily react with other substances. This stability is one of the reasons nitrogen occupies such a significant portion of the atmosphere.

Oxygen, while crucial for life and accounting for about 21% of the atmosphere, is not the majority gas. Carbon dioxide and hydrogen make up a much smaller fraction of the atmosphere, with carbon dioxide currently around 0.04% and hydrogen being less than 0.00005%. Thus, nitrogen is correctly identified as the gas that makes up the majority of the atmosphere.