My time to shine ;)
So.
Basically when we die, our bodies start to decay.
The question is what happens to the atoms in our body.
Well, since we start to decay, the atoms in our body start to "fall apart" or "spread out" because we are decaying.
The atoms might go into the soil, into a plant, or just into the environment.
Here's an example.
We all know what changing states of matter is (it's when a solid, liquid, or gas turns into a different state of mater - pretty self-explanatory)
So, say either a solid or a liquid gets heated up and the particles start to spread out. That's what happens to the atoms.
Now, the "final stage" is when it gets turned into a gas. So when it fully evaporates.
Now the particles in the water vaper is now apart or the atmosphere. Just like how when we die, the atoms spread out and become one with the environment.
Hope this helps your 1 am thinking.
-Pervy Sage-