Question 8: the correct answer is Nitrogen. Got it right? Award yourself 1 point.
Question 9 of 10
What is the largest biome in Brazil?
Why, in question 8: Which gas is the most abundant in the air we breathe?
The answer is nitrogen, which makes up about 78% of the air. Oxygen comes second, at about 21%, and argon at almost 1%. Carbon dioxide is well under 1%, but it has a major effect on the climate.
What is so much nitrogen used for
We breathe nitrogen in and exhale it again without using it. But it is essential to life: it is part of proteins and DNA, and plants need it to grow.
Plants cannot take nitrogen directly from the air. That job is done by soil bacteria, many living in the roots of plants such as beans and soybeans, and by lightning, which converts part of this gas into compounds that reach the soil with the rain.
Nitrogen fertilizers produced by industry, based on a process invented in the early twentieth century, helped multiply food production around the world.
Argon, the third gas in the air, is a noble gas that barely reacts with anything. That is why it is used inside light bulbs and in welding, to protect the metal from oxygen.
