Why is nitrogen the most common gas in the atmosphere?
I guess it is because there is lots on nitrogen on earth and N2 gas is fairly inert, i.e., there are not many things nitrogen reacts with. I think oxygen may be the most plentiful element on earth but it is only 20% of our atmosphere because oxygen is very reactive. The minerals in soil, sand, and rock contain oxygen in compounds including SiO2, CaO, MgO, Fe2O3, & Al2O3 and, of course, earth’s water is H2O. If there was not so much nitrogen in our atmosphere, it might be a problem for plants, plants need nitrogen and you can buy fertilizer with nitrogen in it (in the form of nitrogen compounds). Some plants, like legumes, can take nitrogen right from the air and convert it into nitrogen compounds that other plants can use. If the oxygen content of our air was higher, there would be a lot more fires, anything that caught fire would burn much faster.
