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Jan 1, 1000
Democritus (hypothesis was created in 465BC)
Democritusminiscule quantities of matter is what he called an atom
This is Democritus' atomic theory exactly:
1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position, and arrangement.
His mentor, Leucippus, originally came up with the atomic theory -
James Dalton
Dalton's life
His atomic theory said that elements consisted of tiny particles called atoms. It states an element is one of a kind (aka pure) because all atoms of an element are identical. All the atoms that make up the element have the same mass. All elements are different from each other due to differing masses. -
Robert Millikan
Determined the unit charge of the electron in 1909 with his oil drop experiment at the University of Chicago. Thus allowing for the calculation of the mass of the electron and the positively charged atoms. -
Ernest Rutherford
Used cathode rays to bombard atoms of various elements and showed that the inner structures correspond with a group of lines which characterize the elements
Discovered that the nuclei of certain light elements could be "disintegrated" by the impact of energetic alpha particles. -
J.J. Thomson
discovered electrons and noticed that an atom can be divided
atoms are made of positive cores and negatively charged particles within it
he discovered the Plum Pudding Model before the atomic nucleus was discovered -
James Chadwick
He proved the existence of neutrons.
He established that atomic number is determined by the numbers of protons in an atom.
He also discovered the fourth subatomic particle,the neutron. -
Niels Bohr
In 1913, he passed on to a study of the structure of atoms on the basis of Rutherford's discovery of the atomic nucleus.
He succeeded in working out and presenting a picture of atomic structure that, with later improvements, still serves as clarification on the physical and chemical properties of the elements.
