The Periodic Table

During the 1800s, many new elements were discovered.  However, scientists knew very little about the structure of atoms.  They tried to organise the elements based on their properties and atomic weights.

In 1863, Newlands proposed the law of octaves, which stated that similar properties are repeated every eight elements.  He put the 62 elements known at that time into seven groups according to their atomic weights.  However, after calcium their properties did not match very well within the groups so other scientists did not accept his ideas.

Dmitri Mendeleev produced a better table in 1869.  His table left gaps for undiscovered elements so that the groups of known elements did have similar properties.  He also…