Refer to the diagram to complete the sentence with the correct numbers. when hydrogen shares electrons with oxygen, the outermost shell of the hydrogen atoms are full with electrons and oxygen’s valence shell is full with electrons. because the valence shells of these atoms are full, the atoms are stable. 

Hydrogen is a highly reactive fuel. hydrogen molecules violently react with oxygen when the existing molecular bonds break and new bonds are formed between oxygen and hydrogen atoms. as the products of the reaction are at a lower energy level than the reactants, the result is an explosive release of energy and the production of water. but hydrogen does not react with oxygen at room temperature, a source of energy is needed to ignite the mixture.