The most plentiful element in the universe is hydrogen. The chemical property you're describing is combustibility, or the ability of a substance to burn in the presence of oxygen.

Here's why:

* Hydrogen is highly reactive and readily combines with oxygen to form water (H₂O). This reaction releases a significant amount of energy, which is why hydrogen burns with a blue flame.

* Burning in air is a common way to demonstrate combustion. The oxygen in the air acts as an oxidizer, combining with the fuel (hydrogen in this case) to produce heat and light.

Let me know if you have any other questions!