-
Dec 1, 1000
Democritus 460-370 BC
Democritus proposed that an atom is a hard particle. That it’s made of one material formed into different shapes and sizes. That they are infinite in number, and that they create different materials by joining together. -
Dec 1, 1010
Aristotle 384 BC – 322 BC
Aristotle presented his model of five elements, Earth, Wind Water Fire, and Ether. This was the most widely accepted model at the time. -
Period: Dec 1, 1010 to
322 BC to 1808
-
John Dalton
Dalton suggested that all substances are made up of atoms, small particles that cannot be created, divided, or destroyed.
He suggested that atoms of the same element are exactly alike and atoms of different elements are different.
He said that atoms join with other atoms to form different substances.Also that through chemical reactions, atoms are combined, separated, or rearranged. -
Sir William Crookes
Crooks created a tube where he was able to see a path way where electrons traveled. -
Dmitri Mendeleev
Mendeleeev assembled the first ever periodic table. His table was the base on which the modern periodic table was built. -
J.J. Thomson
Thomson took the Crookes tube, and attempted to direct the particle beam away from its path. He successfully altered the path of the beam with the magnets, and hypothisised that the particles had a negative charge. These particles became known as electrons. -
Ernest Rutherford
Ernest Rutherford was a student of Thomsons, and conducted a study that shot particles through a sheet of gold. He expected the particles to pass cleanly through, but instead, many particles bounced astray. -
Niels Bohr
Bohr created a model of the atom that showed electrons orbiting a center mass, the nucleus. His model is still used to depict the image of an atom today. -
James Chadwick
Chadwick discovered neutrons. His theory was based off experimental findings by Joliot Curie -
Erwin Schrodinger
Schrodinger created the foundation for the wave mechanics approach to quantum theory.
