GCSE AQA Chemistry 1 Elements & Compounds

Atoms
1. Nucleus in the middle
  1. Contains protons & neutrons
    1. Protons = Positive Neutrons = Neutral
      1. Positive charge overall
2. Electrons
  1. Move around nucleus in shells
    1. Negatively charged
3. No overall charge
  1. No. of protons = no. of electrons
    1. Add/remove electrons - atom becomes charged (ion)
Elements
1. Contain 1 type of atom
  1. No. of protons decides type
2. About 100 different ones
The Periodic Table
1. Elements with similar properties in same group/column
  1. All elements in group have same no. of electrons in outer shell
2. Top number: Mass no.
  1. Total no. of protons & electrons
3. Bottom number: Atomic no.
  1. No. of protons (same as no. of electrons)
Electron shells
1. Lowest energy shells always filled first
2. Only certain no. allowed in each shell: 2 in 1st shell, 8 in 2nd shell & 8 in 3rd shell
3. Full shells are ideal
  1. Otherwise will react to fill
Compounds
1. Form chemical bonds with other atoms to make compounds - difficult to separate again
  1. Making bonds: Giving away/taking/sharing electrons
2. Ionic Bonding
  1. Metal & Non-metal -> IONS
    1. Metal atoms lose electrons to form positive ions
      1. Non-metal atoms gain electrons to form negative ions
        Opposite charges strongly attracted to each other
3. Covalent bonding
  1. Non metals -> MOLECULES
    1. Sharing electrons
      1. Makes enough to fill outer shell
4. Properties of compound different from original elements'
  1. Can be lattices/molecules

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GCSE AQA Chemistry 1 Elements & Compounds

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