The element that makes up about 78% of the Earth's atmosphere is nitrogen (N). Nitrogen is a colorless, odorless gas at room temperature and is an essential component of the atmosphere, playing a crucial role in the Earth’s ecosystems. While nitrogen is abundant in the atmosphere, it is relatively inert and does not readily react with other substances. As a result, nitrogen gas must be converted into usable forms, such as nitrates or ammonia, through natural processes like nitrogen fixation, important for the growth of plants. This makes nitrogen a vital element for life on Earth.