Question

Although nitrogen gas makes up 78% of the atmosphere, we can't use it because _____.

A. Nitrogen gas is explosive

B. We must absorb it through the soil

C. Nitrogen atoms must be broken apart first

D. We must absorb it through the sun

Answer 1

C is the answer. nitrogen is very much packed and bonded with its atoms.

Answer 2

C. Nitrogen atoms must be broken apart first

is the answer.

There is abundant of the element nitrogen present here, making upto 78-79% of our atmosphere. But nitrogen (N2) has a very strong triple bond between the two atoms and under normal conditions it won't react with anything and generally can't be used by either plants or animals.

For plants to be able to make use of the nitrogen they need the bond broken and recombined as either ammonia NH3 or NH4 or nitrate NO3, via a process called nitrogen fixation.