Which colorless gaseous element occupies about 4/5 of the air?

Nitrogen is the correct answer because it makes up approximately 78% of the Earth's atmosphere. This colorless and odorless gas is crucial for life as it is a fundamental component of proteins and nucleic acids, which are essential for all living organisms. Nitrogen is relatively inert and does not easily react with other substances, which contributes to its abundance in the atmosphere without causing harmful effects.

Oxygen, while vital for respiration in most life forms, only comprises about 21% of the atmosphere. Carbon dioxide, a trace gas present in the atmosphere, is vital for the process of photosynthesis but accounts for less than 0.04% of the air. Neon, a noble gas, makes up only a very small fraction of the atmosphere and is not involved in biological processes, further distinguishing it from the predominant gaseous components. Thus, nitrogen is clearly the primary gas in the air by volume.