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100
Democritus's view on the Atom
Democritus(c. 460 – c. 370 BCE) believed that everything is made of "atoms"(Greek atomos, indivisble) and these atoms are chemically pure, infinite, , cannot be divided into 2 seperate parts, and that atoms can be different weights and shapes, His picture and view of atoms were inert solids and each atom interacted with other atoms mechanically. -
100
Aristotle's view on the atom
(384 BC – 322 BC)
Philosopher with long list of studies which included chemistry.
He believed that there was 5 pure elements, Earth,Water , Air , Fire, and Aether. According to him these elements made up every known thing. -
Period: 100 to
From Classical Times to the Modern Day
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Antoine Lavoisier and the atom
Changed sciences from qualitative (i.e. getting everything right) to quantitive(i.e. Getting a bunch of measurements and averaging them to get the right answer. Also recognized the elements Oxygen, Hydrogen, Silicon, and Sulfur.
Wrote list of Elements and discovered that whenever matter changes form or shape, its mass stays the same. -
John Dalton and the atom
John Dalton had 5 principles of his atomic theory
1. Elements are made up of atoms
2. Atoms of the same element are the same
3. Atoms cannot be created or destroyed
4. Different atoms can combine to form chemical compounds
5. Atoms are moved or changed in Chemical reactions
He promoted a concept of the atom as a solid positively charged sphere. -
J.J. Thomson and the atom
Discovered electrons by finding that cathode rays were composed of a negatively charged particle. Found out that there were isotopes of Stable elements, and invented the mass spectrometer, a device that allow us to see elemental compositions and thus properties of substances. Supported the "Plum Pudding" model but with electron "raisins" inside it. -
Henri Becquerel and the atom
Co-Founded the Theory of Radioactivity with Marie and Pierre Curie, and helped the discover the element Thorium. -
Robert Millikan and the atom
Robert Millikan used an oil-drop experiment, where tiny particles of oil are charged with electricity and then contrasted with various forces, to discover the charges of particles. He supported though experimentation Einstein's photoelectric theory. -
Marie Curie and the atom
Marie curie and Pierre curie discovered 2 new elements, polonium and radium, ways of isolating isotopes, and radioactivity, which is the decay of heavy atoms into lighter atoms, giving off heat and energy. They worked with Henri Becquerel. -
Ernest Rutherford and the atom
Discovered the comcept of the half-life, differentiated between alpha and beta radiation and pioneered the Rutherford model of the atom, with a nucleus in the middle and the electron revolving in diagonal rings. This contrasted wit hthe plum pudding model as the mass was taken up by the super dense and small nucleus. -
Niels Bohr and the atom
He predicted the existence of Hafnium, and has Bohrium named after him. Developed the Bohr model of the atom, which has the nucleus in the center and rings of electrons in a 2-D circle around it. It contrasts with Rutherford's model as the electrons are in stable and non-moving orbit. Worked with Werner Heisenberg. -
Henry Mosely and the atom
He perfected the atomic number and how to calculate it. Supported Niels Bohr's theories on the shape of the atom. -
Max Planck and the atom
He and the people he worked with, Bohr and Pauli, came up with the Copenhagen quantum theory, -
Erwin Schroedinger and the atom
Studied electron fields of atoms to find out about wave mechanics, which deal with quantum states. Also challenged traditional quatum mechanical thought with His "Schroedinger's Cat", a paradox in which something can be alive or dead at the same time. -
Werner Heisenberg and the atom
Formulated Matrix Mechanics, the first logical part of quantum mechanics. -
James Chadwick and the atom
He discovered the neutron by breaking up atoms using other atoms and trapping pieces of the broken-up atom on paraffin wax. He worked and studied with Rutherford.
