Excess oxygen is actually harmful to humans, but all the climate warnings are about losing oxygen, not nitrogen edit: but when we look for habitable planets, our focus is ‘oxygen rich atmosphere’, not ‘nitrogen rich’, and in medical settings, we’re always concerned about low oxygen, not nitrogen.
Deep sea divers also use a nitrogen mix (nitrox) to stay alive and help prevent the bends, so nitrogen seems pretty important.
It seems weird that our main focus is oxygen when our main air intake is nitrogen. What am I missing?
edit: my climate example was poor and I think misleading. Added a better example instead.
Overall you’re not on a bad track with thinking that other elements in the same column could substitute for nitrogen, often those elements will have similar properties.
However it doesn’t really apply in this particular case, the other elements in its group are all pretty reactive and solid, and include elements like phosphorus and arsenic. Even nitrogen compounds can be pretty damn reactive, it’s just kind of a quirk of chemistry that diatomic hydrogen (N2) which makes up most of our atmosphere is pretty stable and nonreactive under most circumstances.
We need certain nitrogen compounds as part of our biological processes but we don’t get that nitrogen from the air, we get it from food we eat, which ultimately get it from the air mostly from microbes in the soil that are actually able to take nitrogen from the air and turn it into other chemicals.
However since atmospheric nitrogen is, for the purposes of this conversation, inert, you can pretty much replace it with any other nonpoisonous gas, like we often do for deep sea divers, because under high pressure nitrogen will dissolve into our blood and then when we resurface it creates nitrogen bubbles in our blood which is very bad.