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French Chemists
In 1787 French Chemists Antoine Lavoisier, Antoine Fourcroy, Louis-Bernard Guyton de Morveau and Claude-Louis Berthollet worked together to create a list of the 33 known elements of the time. Antoine Lavoisier was convicted traiter 7 years later and guillotined on 8 May 1794. A year and a half after death he was pardoned. -
Johann Wolfgang Döbereiner
Johann Döbereiner found that elements could be organised into groups of three, or triads, due to their similarities. He noticed that when ordered in the triad according to the element's atmoic weight, the middle element's properties were between the first and third elements. Years later Peter Kremer used the triad theory to suggest certain elements could fit into two triads that were placed perpendicularly. This became an important part of Mendeleev's future system. -
Jean Baptiste André Dumas
Dumas turned away from triad theory and instead focused on mathematical equations that could account for increase in atomic weight within groups of chemically similar elements. -
Dmitri Ivanovich Mendeleev
Birth of the "modern" and current periodic table, created by Dmitri Mendeleev. This table ordered the 63 known elements at the time, according to atomic weight. Mendeleev also left spaces for undicovered elements, predicting their atomic weights. -
English Chemists
The two English Chemists William Ramsay and Lord Rayleigh discovered the element argon. William Ramsay then proceeded to discover four other elements: helium, neon, krypton and xenon. These elements are what are now known as the noble gases. The pair received Nobel Prizes in 1904. -
J. J. Thomson
J. J. Thomson discovered the electron years earlier, however created one of the first models of an atom. Thomson believe that electrons were arranged in rings that lay inside the main body of an atom. He also believed that elements with electrons in similar configurations had similar properties. -
Ernest Rutherford
Rutherford created his model of an atom after observing interactions of particles and metals. His data led him to believe an atom had the majorty of it's mass in a small charged nucleus, orbitted by low-mass electrons. In 1920 he stated hydrogen nuclei were an important build block of all nuclei, which he later called the proton. In 1921 he suggested the existance of neutrons whilst working with Niels Bohr, that would explain why a nuclei wouldn't fly apart from the repulsion between protons. -
Henry Moseley
Henry Mosely investigated the hypothesis that the ordering of elements should be in the nuclear charge of an atom. He photograph the x-ray spectrum of 12 elements, discovering that atoms have a quantity that increases in regular steps as elements pass from one to another. Mosely died during World War 1 unfortunatly, due to conscription. -
Niels Bohr
This Danish Physicist constructed a model of an atom that suggested electrons were in shells encircling the nucleus. Bohr stated that elements in the same group may have identical configurations in their outermost shell. His theory explained why the Noble Gases lacked reactivity.
