C4 Revsion

C4 Revsion

1. Atoms

   • The nucleus is positively charged and contains protons and neutrons
   • Electrons surrounding the nucleus are negatively charged
   • Number of protons equals number of electrons
   • Each element has a different number of protons
   • When electrons are added or removed from atom, it becomes charged and an ion
   • Protons=1 relative mass and +1 charge
   • Neutrons= 1 relative mass and 0 charge
   • Electrons= 0 mass and -1 charge

2. Chemical Equations

   • Atoms aren't lost or made in chemical reactions
   • (s)= solid
   • (g)= gas
   • (l)= liquid
   • (aq)= dissolved in water
   • Balance one atom at a time

3. Line spectrum

   • Some elements emit distinctive colours when heated
   • Lithium= Red flame
   • Sodium= yellow/orange
   • Potassium= lilac flame
   • Each element gives a characteristic line spectrum
   • When heated, electrons become excited and release energy as light
   • Wavelengths emitted can be recorded as a line spectrum
   • Different elements emit different wavelengths of light due to different electron arrangement
   • Spectrums can be used to identify elements

4. History of the Periodic Table

   • Doberiner tried to organise elements into triads
     • Put them in groups based on their chemical properties (groups of three)
       • Middle element of each triad had average relative atomic mass that was the average of the other two
   • Newlands' Law of Octaves: every eighth element had similar properties.
   • Mendeleev left gaps and predicted new elements