# What is a combination of chemical symbols and numbers to represent a substance?

$\text{....A chemical formula.......}$
A chemical formula is a shorthand that represents the proportion or number of chemical elements in a compound or molecule. For the molecule $\text{butane}$, we could represent this as ${C}_{4} {H}_{10}$, or we could give a bit more information on the formula:
${H}_{3} C - C {H}_{2} - C {H}_{2} - C {H}_{3}$, which shows the connectivity of the molecule.