- Nitrogen is a kind of gas
- Most means over 50% of something
- The earth 's atmosphere is made of 78 percent nitrogen by mass
- So, nitrogen gas makes up most of the earth's atmosphere

Hence, nitrogen gas makes up most of the earth's atmosphere
Question: Air is made up of many gases. Which gas is found in the greatest amount?
Context: - Nitrogen is a kind of gas 
- Most means over 50% of something 
- The earth 's atmosphere is made of 78 percent nitrogen by mass