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Four Element Theory
330 BC Aristotle came up with the four element theory. This stated that there were four elemnts - fire, water, earth and air. -
First Major List Of Elemnts
1770 AD - Antoine Lavoisier began to write the first major list of the elements. He finished this in 1789 This contained 33 elements that were distinguished between metals and non - metals, although, some of his elements were later found to be mixtures or compounds. -
First Table Of Atomic Weights
1828 - Jons Jakob Berzelius created a table of atomic weights. He was the first person to use letters to symbolize the elements. -
Triads
1829 - Johann dobereiner developed triads. These were three groups of three elements with similar properties. The triads were as follows; lithium, sodium, potassium and calcium, strontium, barium and chlorine, bromine, iodine. Johann was the first man to have the idea of putting the elements in groups. -
Law Of Octaves
1864 - John Newlands created the law of octaves. This identified similarities among the elements, though he did not leave room for the undiscovered elements. This was the first idea of periods. -
Lothar's Table
1869 - Lothar Meyer made a table of 56 elements based on the elements properties. -
Dmitri's Table
1869 - Dmitri Mendeleev, the "father of the periodic table," produced a table with gaps for unknown elements. He could predict the properties of these unknown elements, such as the melting point. -
Discovery Of The Noble Gases
1894 - William Rasmay discovered the noble gases. He was awarded a Nobel prize for this in1904. -
Atomic Numbers
1913 - Henry Moseley found the atomic number for each of the elements. He also modified the Periodic Law to read that the elements' properties vary periodically. -
Moseley's Theory
1914 - Henry Moseley theorised that there were three unknown elements between allumiun and gold. -
Transuranic Elements
1940 - Glenn Seaborg synthesised the transuranic elements, the ones after uranium. In 1951 he was given a Nobel prize for his efforts.
