Atomic History

Atomic History

1. Democritus

   • Came up with the theory that if matter is divided into smaller and smaller pieces, the end product would be tiny, indestructible particles called atoms

2. Dalton

   • 1. Each element is composed of tiny indestructible particles called atoms
   • 2. All atoms of a given element have the same mass and other properties that distinguish them from other elements
     • *mass is incorrect*
   • 3. Atoms combine in simple, whole number ratios to form compounds
     • *Law of Definite Proportions*

3. Thomson

   • Discovered the electron, a negatively charged particle that is even smaller and fundamental
     • Created the plum pudding model with a positively charged sphere with electrons sprinkled in

4. Rutherford

   • 1. Most of the atom's mass and all of its positive charge are contained in a small core called the nucleus
   • 2. Most of the volume of the atom is empty space through which the tiny, negatively charged electrons are dispersed.
   • 3. There are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons) inside the nucleus, so that the atom is electrically neutral

5. Niels Bohr

   • Planetary model

6. Quantum Mechanical Model

   • Electrons exist on quantized energy levels but don't orbit like planets
   • Electrons exist in areas of "probability" called orbitals

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