Chemistry 4-6

Chemistry 4-6

1. Line Spectrums

   • Li = Red Flame
   • Na = Yelllow
   • K = Purple
   • When heated electrons give excess energy out as light.
     • Each element is different
       • So they can be identified by their line spectrum, 3 elements have been found from this Caesium, Rubidium and Helium (from sun)

2. Periodic Table

   • Dobereiner; Tried to organise elements by triads (in threes) the middle one had to be average of the other two.
     • Newland; He tried to organise elements by Rel. Mass. He found that evry eighth element has similar propities but this was broken by Ti and Fe
       • Mendeleev; He organised elements like Newland but left gaps to keep similar elements together. So he PREDICTED elements. which were undiscovered.
   • Electrons
     • Electron Shells Fill across rows
     • 2,8,8
     • Same number of electrons as protons / neutrons

3. Ions

   • Ions are made when atoms gain or lose electrons
   • Group 1 want to lose an electron, Group 8 wants to gain one.
   • When they gain an electron they become NEGATIVE, When they lose one they become positive.
   • Alkali Metals
     • More reactive,higher density, lower melting / boiling point as they go down.
     • Produce hydrogen with water, and salts with chlorine.
   • Halogens
     • Less reactive,higher melting / boiling point as they go down.
     • Non Metals with coloured vapours
   • Positive ions
     • How to spot
       • Flame Tests
       • Precipitate
       • State Symbols
     • Negative Ions
       • How to spot
         • Hydrochloric Acid detects carbonates
         • Sulphates, is HCL and Barium
         • Halides, (Cl-,Br-,I-) Nitric Acid and Silver Nitrate

4. Atmosphere

   • Small molecules (like co2) need little energy to break weak forces, this is why they are gases at RmT
   • Covalent Bonding
     • This is sharing electrons, two atoms share electrons so they have a full shell.
   • Hydrosphere
     • Also known as oceans / water
     • Solid ionic compounds form crystals, these are made of ions they are ionically bonded
       • They have high melting/boiling points
       • They also conduct electric when dissolved / molten
     • Lithosphere
       • Natural Minerals
       • Carbon forms giant structures
         • Graphite
         • Diamond
         • Silicon Dioxide

5. Salts

   • Neutralisation produces a salt
   • HCL will allways produce chloride salt
   • Acid + Metal = Salt + Hydrogen
   • Metal Carbonate + Acid = Salt + Water + CO2
   • Syntheising Compunds
     • 1) Choosing Reaction
       • 2) Risk Assesment
         • 3) Calculate Quantities
           • 4) Choose Equipment
             • 5) Isolate Product
               • 6) Purify
                 • 7) Measure for Yield/Purity
                   • yield = actual yield / theoretical yield * 100
                     • Purity = concentration = conc. * vol. / vol. of solution
                       • 2) mass = conc. X vol
                         • Purity = mass of pure / impure *100

6. Metals

   • Metals are usually found as ore, joined to rock or other compound
   • Mostly the ore is the oxide of the metal
     • Reducing (De-Oxygenating) With Carbon means that carbon is added to produce co2 with the oxygen and freeing the metal
       • Only metals LESS reactive than carbon works
         • Reactivity Series -->
         • For metals MORE reactive than carbon electrolysis is used
           • electrolysis is the splitting of a substance using electric
             • Aluminium need three electrons so it goes to the negative electrode when it gets this it turns wolten as flows to the bottom. The oxygen goes to the positive electrode where it becomes o2 and bubbles away.
   • Reactive metals need chemical reaction to remove this is why sodium took so long to discover.
   • Metals get their propities due to the electron cloud
     • Properties:
       • Conduct heat / electricity
       • Strong and maluble under heat.

7. Energy Transfer

   • Endothermic = GAINS ENERGY
   • Exothermic = RELEASES ENERGY

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