Answer: Nitrogen
Explanation: The atmosphere surrounds the Earth as a layer composed of different gases, which is known as air. The Earth's atmosphere is maintained by gravity, and the significance of the atmosphere is multiple. Thanks to it on earth there is a possible life, it allows the running water to exist on the surface. In addition, it keeps ultraviolet radiation and heats the surface of the earth by producing a greenhouse effect, which is not harmful to a moderate extent. The atmosphere consists of 78% nitrogen, 23% oxygen, argon 0.9-1%, carbon dioxide 0.03% and a very small percentage of other gases.