Chemical formula that compound will be made up of the same elements in the same proportion or ratio. For example, any water molecule is always made up of two hydrogen atoms and one oxygen atom in a 2:1 ratio. If we look at the relative masses of oxygen and hydrogen in a water molecule, we see that 94% of the mass of a water molecule is accounted for by oxygen and the remaining 6% is the mass of hydrogen. This mass proportion will be the same for any water molecule. The alkene called but-2-ene has two isomers, which the chemical formula CHCH=CHCH
Chemical formula number of repeating units is unknown or variable, the letter "n" may be used to indicate this formula: CH(CH)CH. For ions, the charge on a particular atom may be denoted with a right-hand superscript. For example, Na, or Cu. The total charge on a charged molecule or a polyatomic ion may also be shown in this way. For example: HO or SO. Note that + and - are used in place of +1 and -1, respectively. For more complex ions, brackets [ ] are often used to enclose the ionic formula, as in [BH], which is found in compounds such