There are two atoms in one hydrogen molecule.
Explanation:
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In this case, when going over chemical reactions, we need to realize about the amount of atoms of each element; thus, according to the given chemical reaction by which water is formed:
It is seen there are two hydrogen atoms in the hydrogen molecule, two in oxygen and two hydrogen atoms and one oxygen atom in water; however, these reactions must be balanced according to the law of conservation of mass:
Which means we have two hydrogen molecules with two atoms each, one oxygen molecule with two atoms and two water molecules with two hydrogen atoms and one oxygen atom each.
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