Nitrogen

Nitrogen is the most abundant element in the atmosphere, making up about 78% by volume of the air that surrounds the Earth. The element is much less common in the Earth's crust, however, where it ranks 33rd (along with gallium). Scientists estimate that the average concentration of nitrogen in crustal rocks is about 19 parts per million, less than that of elements such as neodymium, lanthanum, yttrium, and scandium, but greater than that of well-known metals such as lithium, uranium, tungsten, silver, mercury, and platinum.

The most important naturally-occurring compounds of nitrogen are potassium nitrate (saltpeter), found primarily in India, and sodium nitrate (Chile saltpeter), found primarily in the desert regions of Chile and other South American nations. Nitrogen is also an essential component of the proteins found in all living organisms.