Atomic Structure & The Periodic Table

Atomic Structure & The Periodic Table

1. Key Words

   • Atom: The smallest part of an element that can exist
   • Element: A pure chemical substance made of only one type of atom
   • Molecule: A group of two or more atoms held together by chemical bonds
   • Compound: Two or more different types of atoms joined together by chemical bongs
   • Mixture: Two or more different type of atom or molecule mixed together, but not bonded

2. Developing the Atomic model

   • The Greek idea of invisible atoms is no longer acceptable as new technology makes it possible to see them
   • Thomson discovered the Electrons
     • Electrons have a negative charge
     • Tomson's model of the atom was called the Plum Pudding model
   • Rutherford fired Alpha particles at his experiment
     • He fired the particles at thin gold foil sheets
     • His experiment showed that atoms are mostly empty space

3. The scientists involved in the development of the atom

   • 500BC- Leucippus & Democrites. They believed that all matter was made up of particles so small they could not be divided.
   • 1800- John Delton. Atoms are the smallest divisions of matter. In chemical reactions atoms rearrange themselves. This helped to develop the periodic table
   • 1897- Joseph (JJ) Thomson. Using cathode rays and deflecting the beam using magnets he discovered atoms contained negative charged particles. The plum pudding model was a a large ball of positive matter with negative charge dotted throughout