Atomic number and mass number

The periodic table shows the unique symbol of every element, together with its mass number and atomic number. For example, lithium (Li) has a mass number of 7 and an atomic number of 3

The picture below will help you to remember which number is which.

A memory aid showing that the mass number is always sown above the atomic number which should be smaller — A bull mastiff (mass) dog is sitting on top of a tom (atomic) cat. The mass number is always the bigger number.