For example, the mass number of argon atoms and calcium atoms can both be 40. The symbol for an atom can be written to show its mass number at the top, and its atomic number at the bottom.

Symbol: A one or two-letter abbreviation used to represent the element. Atomic number: The number of protons in the nucleus of an atom of the element ... than atomic mass. This arrangement ...

according to increasing atomic number. Scientists use the periodic table to quickly refer to information about an element, like atomic mass and chemical symbol. The periodic table’s arrangement also ...