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Democritus
He was the first person to suggest that matter could not be infinitely divided. He came up with the name atom. He couldn't figure out what holds the atom together. -
John Dalton
Dalton took Democritus' ideas and created the phrase "Atoms are the smallest particles of matter and are invisible and indestructible." -
J.J. Thompson
He designed a series of Crt experiments to determine the ratio of the particle's charge to mass. -
Robert Millikan
He designed an oil drip apparatus to determine the charge of the electron. He also determined that the magnitude of the charge of the electron was 1.602x10^-19 coulombs. He also discovered the mass of the electron using the known charge/mass ratio: 9.1x10^-28 g. He made the Plum Pudding Model. -
Ernest Rutherford
Rutherford tested the Plum Pudding Model and found that some a-particles bounced back, therefore causing the model to be incorrect. He studied how positively charged a-particles interacted with solid matter. He came to the conclusion that there had to be a place for the positive charge and the majority of the mass of an atom to reside. Because he realized this, he discovered the nucleus. -
James Chadwick
James Chadwick found that the nucleus had another neutral subatomic particle. He won a nobel piece prize for discovering the nuetron. -
Aristotle
He disagreed with Democritus' idea that atoms move through empty space. Due to personal ideas about nature, he completely denied the existence of atoms. HIs ideas took over those of Democritus.
