Mendeleev organized the chemical elements based on their

Mendeleev organized the chemical elements based on their properties.

Mendeleev put elements in order in the periodic table according to their physical and chemical properties. He noticed that properties of elements were related to their atomic mass in a 'periodic' way, so he groups of elements with similar properties into vertical columns in the table. His periodic table had initial 63 elements which then expanded to 108 or 109 elements.