My Answer:
Nitrogen Gas (N₂) / Nitrous Oxide (N₂O)
Or Helium!!!
We love it...
Also known as laughing gas (N₂O that is)...
Helium is so light it floats out of our atmosphere...
Kids and adults like breathing it or using it in balloons
Its colourless...
It splits into two...
It is found above (70% of the atmosphere)...