Oxygen
imagine if all the oxygen was disappeared not forever just for 5 seconds, what will to the atmosphere, what would happen to the environment. take a deep breath the more you taking is 21% of oxygen in our atmosphere 78% being nitrogen, although it's not the most abundant gas in our atmosphere. It is the most important. Without oxygen, plants, animals, water and us humans wouldn't be where we are today. 5 seconds may not sound like a whole lot of time to be without oxygen. Most of us can go at least 30 seconds without taking a breath. So it would happen too fast for your body to even notice your breathing would actually remain normal.
But as for everything else, not so much. In just five seconds, the Earth would look completely different. Without oxygen, you can say goodbye to the Hoover Dam, the pantheon dome and anything else made of concrete. These structures would instantly collapse. Oxygen acts as a special binding agent to concrete without it. Concrete is just dust. Speaking of buildings, any untreated metal would instantly be fused together. This is because there's a layer of oxidation on metals that prevent them from welding together without that layer. Metals would instantly bind to each other. There would be nothing protecting us from the sun's UV rays. In addition to a sunburn, our inner ear would explode, losing oxygen means losing 21% of our air pressure.
A change in air pressure that drastic is equivalent to being at sea level and dropping down 2000 meters instantly. Our ears wouldn't have enough time to adapt. Having a good time yet. Well, don't expect it to last long without oxygen.
There's no fire. The combustion process and vehicles wouldn't be able to occur. Any mode of transport that is an electric will automatically fail. Planes will fall from the sky, and millions of cars will be stopped in their tracks. The sky would be completely dark before. It hits the earth, like from the sun bounces off multiple particles in the air without oxygen in the atmosphere. There are less things to bounce off, and the sky will appear dark. Oh yeah.
And while all this is happening, the Earth's crust would completely crumble. That's because Earth's crust is made up of 45% oxygen. The crust would crumble and continue to crumble until there's nothing left, sending you and everyone on the planet into a free fall. Sound like fun? Probably not. But luckily, you can take a deep breath of 21% oxygen, knowing this will never happen.