Use the chemical reaction to answer the question.

There are four atoms of hydrogen (HH ) before the reaction. How many atoms of hydrogen are present
after the reaction?
2H2 + O2 → 2H2O 2H2 + O2 → 2H2O

After the reaction, there are still four atoms of hydrogen present. This is because the hydrogen atoms in the reactant molecules (2H2) combine with the oxygen atom (O2) to form water molecules (H2O), but the total number of hydrogen atoms remains the same.