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400
Democritus 400 B.C.
Democritus had the theory that tiny indivisible and destructible spheres existed known as atoms. His idea was flawed though because he had no actual evidence or experimental data to explain his idea as later Dalton would. -
Robert Boyle
Proved the inverse relationship between the volume of a gas and it’s pressure. Known as Boyle’s Law. -
Antoine Lavoiser
Gave modern explanations to processes like combustion, respiration, and calcination and oxidation of metals. Had concepts to acids, bases, and salts. -
John Dalton
Transformed the ideas that democritus had into scientific theory by using experimental methods.
1. all elements are composed of tiny indivisible particles called atoms
2.atoms of the same element are identical
3. atoms of different elements can physically mix together or can chemically combine
4. chemical reactions occur when atoms are separated, joined, or rearranged -
Dmitri Mendeleev
Developed the periodic table. Based on atomic weight. Helped predict undiscovered elements based on the setup of his periodic table. -
Eugen Goldstein
Used a cathode ray and discovered that there were particles traveling in the opposite direction with a postive charge called protons. Similar to Tomsons experiment. -
J.J. Thomson
J.J. Thompson built a cathode ray tube with an anode (positive) on one end and a cathode (negative) on the other. When he passed the electric current through the trapped gas he found that the particles were attracted to the positive, which is how he discovered the electrons or negatively charged subatomic particles. -
Max Planck
Energy did not flow steadily, but in discrete packets. Also known as quanta. Revolutionized physics. -
Ernest Rutherford
Rutherford performed the "Gold Foil" experiment where he shot a a ray of alpha particles at a thin sheet of foil to see what would pass through and what would bounce back. Rutherford discovered that an atom is made of mostly of empty space as most of the particles passed through the sheet, bit a little bit bounced back at large angles. This is how Rutherford discovered that the atom has a nucleus and the rest is empty space. -
Henry Moseley
Measured x-ray spectra of different chemical elements by diffraction in crystals. Because of this, he discovered a systematic relation between wavelength and atomic number. Known as Moseley’s Law. Made sorting out chemical problems quickly. -
Robert Millikan
He carried out an experiment to try to figure how much a charge was. He discovered that there are no fraction in charges and that they are always whole numbers. He performed the oil drop experiment to discover the mass of the electron as well. -
Niels Bohr
Added onto Rutherford’s work, saying the electrons existed at set levels of energy. If atoms absorbed energy, the electron got a level further from the nucleus. If the atom radiates energy, the electron gets closer to the nucleus. -
Erwin Schrodinger
He was made famous for Schrodingers equation which allowed people to measure wavelengths and therefore promoted the electron cloud model. The equation shows that a person can only predict the place where an electron might be and find the probability that it’ll be there, but cannot pinpoint the exact location. -
James Chadwick
He discovered and confirmed the existence of the neutron. He also contributed to the making of the atomic bomb. He used a similar experiment to Rutherford's to confirm the theory.
