Hydrogen has 1 electron in its valence shell, while oxygen has six, this gives hydrogen one bonding spot and oxygen two bonding spots so the two elements are always combined in a two to one ratio in a bent molecule that we call water.
Hydrogen is a nonmetal gas as it oxygen but when they combine, they form water which can exist in all three states in the range of conditions that are on earth. These two atoms require a great deal of energy to be bonded together.
This energy is released in the form of an explosion thats only by product is water. These two elements also form hydrogen peroxide but that is not with elemental oxygen, it is with oxygen’s negative polyatomic ion.
Hydrogen is a highly explosive gas that in almost all of its reactions, explodes because its electron is in the 1s orbital and it often bonds with things in 2p and greater orbitals as is the case with water.
This is a very large energy change which causes the explosion and is what I think may have caused the big bang when some hydrogen and nitrogen tried to get together and they accidentally blew up into this universe. There are some things that we will never know and that is one of them and I think that the big bang is one of them.
But one of the things we do know is that electrons moving between energy levels during bonding often leads to explosions as is the case on the reaction that forms water.
The explosion that creates water is the thing that all life is based on. If those two elements could not combine, then we would not be here nor would anything else that is alive be here.
The explosive nature of hydrogen and oxygen is what is keeping us from using it as auto fuel. In order to be used as auto fuel, that car must be able to withstand very high temperatures and a high energy explosion. Other than that, hydrogen would be an excellent fuel for all veihicles and the only by product is water.
Well there is one other problem, where do you get hydrogen as none of it occurred freely on earth and we will need to go to space to get it, so that would make the fuel quite expensive but still probably cheaper than oil though we will see how everything goes with this in the near futire.