The Structure Of An Atom.

The Structure Of An Atom.

1. Electrons

   • Have a relative charge of -1
   • Electrons are held in shells

2. Neutrons

   • The Neutrons are found in the nucleus
   • Neutrons are neutral, they have no charge

3. Protons

   • The Protons are found in the Nucleus
   • Have a relative charge of +1
   • The number of protons in an atom is its atomic number

4. The Structure

   • The Neutrons and Protons are found in the nucleus which is at the centre of the diagram.
   • Electrons are around the nucleus in shells.
   • Depending on the shell, it depends how many electrons fit onto it.
     • The first shell around the nucleus can hold up yo 2 electrons, the second and third can hold up to 8
   • The number of protons is always the same as the number of electrons
   • The number of electrons on the outer most shell shows what group the element is in
     • For example, in this diagram, there are 6 electrons on the outer ring, this means it must be in group 6 on the periodic table.
     • If you count up the number of electrons on the diagram, it equals the atomic number of the element

5. Example

   • This atom diagram has the electron number - 2,8,1
   • It has 3 shells and the last shell has 1 electron on it, this means it is in group 1 on the periodic table
   • The total number of electrons is 11. This means the element must be Sodium.

6. Theories

   • Dalton
     • He came up with some theories in the 1800's. He did many tests and came to these main conclusions
       • All matter is made of atoms
       • Atoms can't be made any smaller
       • Compounds are made when 2 or more atoms are joined together
   • JJ Thompson
     • He discovered the electron in 1897. He found out that atoms could be broken into smaller peices.
   • Rutherford
     • In 1911 Ernest Rutherford used experiments to show that an atom contains a central nucleus. This supported the fact that an atom can be broken into smaller pieces.
   • Bohr
     • Neil further developed Rutherford idea of the atomic model. He found out that electrons orbit the nucleus in shells.

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