H Chem: Chapter 4 (Day 1) - Development of the Atomic Theory

• ​300 BC

• ​Greek Philosopher

  • ​All matter was made of small, indivisible particles called atomos

  • ​Atomos means unbreakable.

• ​First to experimentally support an atomic theory.

  • ​Law of Multiple Proportions

  • Law of Definite Proportions

  • ​Law of Conservation of Mass

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​He developed the Solid Sphere Model

• ​All elements are composed of tiny indivisible particles called atoms.

• ​Atoms of the same element are always identical.

• ​Atomis cannot be subdivided, created, or destroyed.​

• Atoms of different elements can chemically combine in simple whole-number ratios to form compounds.

• ​Chemical reactions occur when atoms are separated, joined, or rearranged, but the atoms themselves are not changed.

• ​Dalton was not quite right ....​

• ​Atoms are divisible.

• ​Elements can have atoms with different masses.

• ​Matter can be created or destroyed in nuclear chemistry

• ​1897

• ​He proposed that the cathode ray was made of small, negatively charged particles called corpuscles (later changed to electrons).

• ​Discovered the charge of the electron

​Negatively charged particles floated through the rest of the positively charged atom.

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​Sometimes called the chocolate chip cookie model.

• ​He was a student of Thomson and proposed that something dense and moving very fast should be able to punch through the Plum Pudding Model.

• ​He developed the Gold-Foil Experiment.

• ​He predicted the existance of the neutron. He is given credit for discovering the nucleus and the proton.

• ​He proposed a different model of the atom.

• ​All of the positive charge is concentrated in one small area in the center of the atom.

• ​Electrons orbit the nucleus like planets in the solar system (this is the nuclear model).

• ​He is given credit for the discovery of the neutron and isotopes.

• ​1913

• ​Studied hydrogen, he specifically looked at the colors of light emitted by hydrogen.

• ​He found that electrons in hydrogen atoms could only exist at certain distances from the nucleus and when electrons move between the "orbitals" absorbed and released energy.

• ​Electrons could only exist in one specific "quantum states".

• ​BUT ...

• ​This only works for Hydrogen

​1926

• ​Using mathematics, Schroedinger could describe where the electrons are in terms of probabilities.

• ​Electron "Clouds" show the location where there is a high probability of finding electron.

• ​Developed the quantum model