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Period: to
Time
All dates have been given to 1st January unless a more accurate date is known. -
Dalton's Atomic Theory
John dalton proposed that all matter is made from tiny particles called atoms -
Triads
In 1829, Johann Dobereiner started the work that led to his theory of triads. This had him showing that certain groups of 3 elements showed trends in a variety of properties. It worked for Lithium, sodium and potassium, Chlorine , Bromine and Iodine, and a few other sets of elements. -
Octaves
John Newlands was the first chemist to come up with a table of the elements. He noticed that several properties repeated every eight elements, if they were ordered by atomic weight. He called this the law of octaves. However this only worked for the first few elments, and people did not believe him. -
Periodic table
In 1869, Dmitri Mendeleev pubkished his periodic ttable of all the known elements. He ordered them by atomic weight and suggested that properities repeat periodically. He also left gaps for elements that had not been discovered yet, which was controversial. he also predicted properties for these elements. -
Gallium Discovered
Mendeleev's Ekaaluminium discovered thsi year -
Scandium Discovered
Mendeleev's Ekaboron discovered this year -
Germanium Discovered
Mendeleev's EkaSilcon discovered this year -
Discovery of the electron
J J Thompson discovered that a negatively charged particle of low mass existed. It was called the electron. -
The nucleus is discovered
Ernest Ruttherford and his team discovered that atoms have a small, dense region at their centre called the nucleus. -
Shells discovered
Niels Bohr first proposed that electrons orbit the nucleus in fixed shells.
