Dmitri Mendeleev was one of the great chemists of the 19th century. He correctly predicted the properties of more than three undiscovered elements. His contributions to chemistry won him the title of the father of the modern periodic table.

Dmitri Mendeleev's Periodic Table was the most scientific periodic table in his time, which led to the formation of the modern periodic table. Mendeleev not only group the elements that shared similar properties but also correctly predicted the properties of undiscovered elements. And this was groundbreaking.

Lothar Meyer's periodic table was a raw version of the periodic table. He successfully classified the elements according their valency with the increasing order of atomic weights. He also depicted the periodicity from his atomic volume vs atomic weight graph.

Newlands' Law of Octaves proposed by John Newlands explains the periodic repetition of physical and chemical properties. The law has many limitations, which are discussed in this article.

De Chancourtois's helical periodic table was the first periodic table that introduced the notion of the periodicity of elements.

Dobereiner's Triads or the law of triads divides elements showing similar properties into groups of three.

The Hund rule of maximum multiplicity states the electrons fills the degenerate orbitals singly before getting paired.

Robert Boyle was a chemist of the 17th century and a founder of the modern chemistry.

Pauli Exclusion Principle: An orbital cannot take more than two electrons.

The aufbau principle provides a helpful rule in the ordering of atomic orbitals.