In what way is the periodic table periodic?

It is periodic as the chemical elements have chemical properties which repeat in an order. The chemical properties of a substance depend on the valence electrons and these are the same for all elements in the group so all elements in the same group have the same chemical properties. read more

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configurations, and recurring chemical properties. This ordering shows periodic trends, such as elements with similar behaviour in the same column. read more