In 1669, German merchant and amateur alchemist Hennig Brand accidentally discovered phosphorus while attempting to create a Philosopher's Stone by heating residues from boiled urine.

In 1789, French chemist Antoine Lavoisier attempted to categorize elements into metals and nonmetals based on their properties.

British natural philosopher John Dalton published a method to determine provisional atomic weights for known elements. His atomic theory, based on stoichiometric measurements, was widely accepted by chemists in the early 19th century.

British physician and chemist William Prout observed that atomic weights appeared to be multiples of hydrogen's weight. This observation contributed to the development of atomic theory and understanding of elements.

German physicist Johann Wolfgang Döbereiner began classifying elements into groups of three, known as triads, based on their related properties. He observed that the atomic weight of the middle element in a triad was often the average of the other two.

In 1829, John Dobereiner introduced the concept of triads in chemistry, grouping elements into sets of three based on similar properties. This was an early attempt at organizing the elements and contributed to the development of the periodic table.

John Newlands, a British chemist, noticed similarities between elements with atomic weights that differed by seven, naming it The Law of Octaves. He drew a comparison with music octaves.

In 1860, the first international conference of chemistry held in Karlsruhe, Germany, introduced a revised list of elements and their atomic masses. It was decided that hydrogen would be assigned an atomic weight of 1, serving as a reference point for determining the atomic weights of other elements.

Alexandre-Émile Béguyer de Chancourtois devised a three-dimensional chart called the 'telluric helix', where elements arranged by atomic weights displayed similar properties at regular intervals.

In 1863, John Newlands observed that the properties of elements repeated every seven elements, which he called octaves. However, his idea was not widely accepted as the pattern did not hold true for all elements.

John Newlands observed that elemental properties repeated every seventh element, similar to how musical notes repeat every eighth note.

In 1865, 27-year-old John A. R. Newlands proposed the Law of Octaves in a letter to the editor of the journal Chemical News. He suggested that elements arranged by their equivalents showed a pattern where elements in the same group appeared on the same horizontal line, with differences in numbers akin to musical octaves.

In 1868, Julius Lothar Meyer created a more developed periodic table listing elements in order of atomic weight, with elements of the same valency arranged in vertical lines, similar to Mendeleev's table.

Dmitri Mendeleev presented his periodic table on March 6, 1869, which organized elements based on atomic weight and left gaps for undiscovered elements, unlike other scientists like Newlands who did not leave gaps.

In 1870, Mendeleev adjusted the positions of some elements in his periodic table, realizing that some relationships were missing due to undiscovered elements. He also changed the valency of certain elements based on his observations.

Mendeleev predicted eighteen elements in his 1871 table, leaving spaces for undiscovered elements. Only half of his predictions corresponded to elements that were later discovered.

Mendeleev's Periodic Table was published in the German journal Annalen der Chemie und Pharmacie in 1872. The table included column headings in German, indicating rows and groups, and atomic masses were displayed increasing from left to right.

Gallium, an element with properties similar to those predicted by Mendeleev for eka-Aluminum, was discovered in 1875.

Eka-boron was discovered in 1879 and later named scandium.

In 1881, Mendeleev and Meyer had an argument over the priority of the periodic table, which led to an exchange of articles in the British journal Chemical News.

In 1882, the Royal Society in London awarded the Davy Medal to both Mendeleev and Meyer for their work in classifying the elements.

In 1884, John Newlands was asked to give a lecture on the Periodic Law by the Chemical Society, which was a recognition of his contribution to the field of chemistry.

Germanium, an element with properties similar to those predicted by Mendeleev for eka-Silicon, was discovered in 1886.

Despite the limitations of his table, John Newlands was recognized for his idea of classifying elements into octaves by the Royal Society of London in 1887.

In 1888, Swedish physicist Johannes Rydberg observed that the atomic numbers of noble gases were related to doubled sums of squares of simple numbers. This finding led to the repositioning of noble gases on the periodic table and the emergence of the octet rule.

By 1890, Mendeleev's periodic table had been universally recognized as a piece of basic chemical knowledge.

In 1894, Lord Rayleigh discovered the noble gas, a significant addition to the periodic table. Noble gases are a group of elements with low reactivity and were a crucial discovery in the field of chemistry.

In 1897, English physicist J. J. Thomson first discovered electrons, leading to further research on atomic structure and the development of atomic theory.

In 1898, British chemist William Ramsay discovered krypton and xenon, along with metargon and neon, using fractional distillation to separate air components. These inert gases were placed in a single column in the periodic table.

In 1900, Ramsay and Mendeleev discussed the new inert gases and their location in the periodic table. Ramsay proposed placing these elements in a new group between halogens and alkali metals, to which Mendeleev agreed.

In 1902, Mendeleev added the inert gases to the periodic table as group 0, following the suggestions made by Ramsay and Errera. This addition did not disrupt the fundamental structure of the periodic table.

In 1905, Swiss chemist Alfred Werner identified the rare-earth elements (lanthanides) and filled the gap in Mendeleev's periodic table. This discovery led to a reorganization of the table and the introduction of the 32-column form.

In 1910, William Ramsey made and characterized radon, adding to his discoveries of noble gases.

Henry Moseley's research on X-ray wavelengths led to the accurate determination of atomic numbers, restructuring the periodic table based on atomic numbers rather than atomic weights. This resolved inconsistencies in chemical properties and confirmed the invalidity of certain claimed discoveries.

In 1914, Ernest Rutherford first identified protons in the atomic nucleus and conducted experiments that led to the understanding of atomic structure and elements.

Henry Moseley, a promising scientist who made significant contributions to the understanding of atomic structure, was tragically killed by a sniper in Turkey during World War I on August 15, 1915.

In 1921, British chemist Charles Bury coined the term 'transition metal' to describe elements between groups II and III in the periodic table. He explained their chemical properties based on the filling of inner subshells, following the work of Gilbert N. Lewis.

Around 1925, the periodic table underwent changes by adding extra columns labeled 'A' and 'B' to the existing groups I-VIII. This transition rearranged elements in new periods and groups, providing a more comprehensive structure.

In 1932, James Chadwick discovered neutrons, completing the basis for the periodic table and contributing to the understanding of atomic nuclei and isotopes.

In 1944, Glenn Seaborg discovered the lanthanide and actinide series in the periodic table. This expanded the understanding of the elements and their placement in the table.

In 1945, American chemist Glenn T. Seaborg introduced the concept of the actinide series, suggesting a new inner transition series similar to the lanthanides. This proposal reshaped the periodic table and clarified the electronic structure of heavy elements.

Following the acceptance of the actinide concept by Seaborg, the groundwork for discoveries of heavier elements led to the discovery of berkelium in 1949.

A publication edited by K. M. Kedrov in 1958, focusing on the periodic law in chemistry.

Until around 1960, a rectangular table derived from Mendeleev's periodic table and focused on reactivity was commonly used in chemistry lecture halls. This table was a standard visual aid for teaching chemistry.

An edited work by D. I. Trifonov from 1981, discussing the history and modern aspects of periodicity.

In 1998, the Royal Society of Chemistry placed a blue commemorative plaque at John Newlands' birthplace, recognizing him as the discoverer of the Periodic Law for the chemical elements.

The discovery of tennessine in 2010 filled the last remaining gap in the seventh period of the periodic table.

In 2011, a Periodic Table Project was undertaken which included creating a wall mural, a free mobile app, and classroom posters.

An article by Pieter Thyssen and Koen Binnemans published in 2015, exploring Mendeleev's role in the Rare-Earth Crisis.

In 2019, the Year of the Periodic Table was celebrated with a unique approach of deconstructing the table into the years the elements were discovered.

The modern periodic table arranges elements based on their atomic numbers and periodic properties. It allows scientists to analyze reactivity, predict chemical reactions, and understand trends in periodic properties.