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Democritus
Democritus believed matter could not be divided into smaller pieces forever, eventually the smallest possible piece would be obtained. This piece would be indivisible. He came up with the name "atomos". -
John Dalton
John believed multiple things that helped propose the atomic theory. He stated through years of research that elements are made up of atoms, atoms cannot be created, atoms made up of the same element are the exact same, atoms of differing elements cannot be identical, atoms combine together to create compounds. Even though some of this imformation was proven false it was a great start to the atomic theory.
Shortcomings- atoms can be destroyed by nuclear reactions. -
JJ Thompson
Thomson showed that cathode rays were made up of a negatively charged particle, he is credited with the discovery and identification of the electron.
Shortcomings- his theory just didn't make sense. -
Marie Curie
Marie Curies theory stated that radioactive particles cause atoms to break down, then releasing radiation that takes the form of energy and subatomic particles. They discover this in 1898.
Shortcomings- Some compounds has stronger radiation. -
Albert Einstein
He found a way to prove that atoms existed.He also had very strong evidence to show how atoms are structured.
Shortcomings- couldn't determine size of atoms. -
Neils Bohr
Niels discovered the Bohr model which proves that the atom has a small positively charged nucleus. Electrons surrounds the nucleus and they travel around it in a circular orbit. This was a huge contributer to the atomic theory.
Shortcomings- incorrect value, thought neutrons were bigger. -
Robert Millikan
He performed the Oil drop Experiment. This helped in determining the charge and mass of an electron. He took awhile to discover this theory, he took from 1908-1917.
Shortcomins- failed multiple times before completing it. -
The electron cloud model
The electron cloud model is an atom model where electrons are no longer described as particles moving around the nucleus in a fixed orbit. It states that the most likely locations of electrons in atoms. -
James Chadwick
James predicted the atom would have a neutron.
He established that atomic number is determined by the numbers of protons in an atom. He also discoverd the neutron -
Ernist Rutheford
Ernest Rutherford discovered the chemical element rutherfordium. Ernest Rutherford was a chemist and physicist. He was born on 30th August 1871 and died on the 19th of October 1937. Ernest Rutherford publishes his atomic theory describing the atom as having a central positive nucleus
surrounded by negative orbiting electrons. Shortcomings- He didn't specify that the atom didn't have specific radius -
Aristotle
Aristotle didn't believe the ancient Greek theory of atoms being different sizes, regular shapes and being in constant motion. Aristotle's theory was used for almost 2000 years, until after the scientific revolution, when other theories were figured out and then started being used. 384-322 BC.