The Periodic Table

The periodic table was discovered by Dmitri Mendeleev in 1869. He put the elements in order of proton (atomic) number and placed them in rows called periods and into vertical columns called groups.

The elements on the left hand side of the periodic table are metals whereas the elements on the right hand side are non-metals.

The group number tells us how many electrons are in the outer shell and the patterns that we see in the groups enable us to predict the properties of the elements in the group.