Historical Development of the Periodic Table

The history of the development of a systematic pattern for the elements dates back to the mid-1800s. Lavoisier made the first attempt at the classification of Elements. The known elements at the time were classified into metals and non-metals. John Dalton, J öns Jacob Berzelius, Dobereineirs, John A Newlands and Julius Lother Meyer also worked on the systematic classification of the Periodic table.

In 1869, Demitri Mendeleev, a Russian Chemist produced the first periodic table of the chemical elements.  He arranged the elements into eight vertical columns, placing them in order of their increasing relative atomic mass.

Mendeleev’s Periodic Law states that when elements are arranged in order of their relative atomic mass, similar properties recur at regular intervals. 

Mendeleev’s periodic table had many gaps, he predicted that there were undiscovered elements which could fill the gaps.  Later elements such as scandium, gallium and germanium etc were discovered, which not only fitted exactly, into Mendeleev’s table but also had the properties he predicted.

But in the modern periodic table, the elements are arranged in increasing order of their atomic numbers. The atomic number of a chemical element has been found to be a more important property of the element than the relative mass of the element.

The Modern Periodic Law states that the properties of the elements are a periodic function of their atomic number. By atomic number, we mean the number of electrons around the nucleus of the neutral atom of the elements and this is equal to the number of protons in the nucleus. 

Periodicity is the repetition of properties of elements after a certain interval when arranged in increasing order of their atomic number.

This leads us to the Law of Periodicity which states that the physical and chemical properties of the elements recur systematically and predictably when the elements are arranged in order of increasing atomic number.