Answer: The number is 2.
Explanation: The molecular formula of water is [tex]H_2O[/tex]. It contains two atoms of hydrogen and one atom of oxygen.
Thus there is an odd number of oxygen atom. To make the atoms even , with the smallest number, we multiply the formula by 2. The number of oxygen atoms in 2[tex]H_2O[/tex] will be 2 , which is an even number.
