Atomic Structure

Atomic Structure

1. Nuclear atom

   • Protons and neutrons make up nucleus at centre
     • Small and dense
     • Mass almost completely in middle, in nucleus
   • Electrons orbit nucleus
     • In shells
   • Most of an atom is empty space
     • Between nucleus and shells

2. Atom's overall charge is zero

   • Nucleus = positive charge
   • Negative charge spread around outside of atom

3. Isotopes

   • Same element
     • Different mass number, same atomic number
     • Different number of neutrons
     • Same number of protons and electrons
   • Same chemical properties
     • Isotopes of same element react in same way
     • Because same number of electrons

4. Ions

   • Charged because they have different numbers of protons and electrons
   • Low electrons = positive charge
   • Gain electrons = negative charge

5. Development

   • John Dalton thought electrons were solid spheres
   • JJ Thompson came up with plumb pudding model
   • Rutherford discovered nucleus

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