Module C4: Chemical Patterns

Module C4: Chemical Patterns

1. Atoms

   • The Nucleus
     • Protons and Neutrons
       • Protons = heavy and positively charged.
         • Elements have different numbers. All Atoms of same element have same number
       • Neutrons = heavy and no charge
     • Positively Charged
     • Tiny, almost whole mass
   • The Electrons
     • move around nucleus
     • negetively charged
     • No mass
     • Arranged in Shells
     • if added or removed atom becomes an ion (charged)
   • Number of Protons = Number of Electrons
     • Same sized charge but opposite

2. Chemical Equations

   • Same atoms at start and end of reaction just rearranged
     • Must be same amount of atoms on both sides of equation
   • Physical States
     • (s) = solid
     • (l) = liquid
     • (g) gas
     • (aq) = dissolved in water

3. Line Spectrums

   • Some Elements produce flames with distinctive colours
     • Li = red flame
     • Na = yellow/ orange flame
     • K = lilac flame
     • different colours in fireworks
     • help chemists to idendity metal in compound. Burn substance, see colours produced.
   • Each Element gives a characteristic Line Spectrum
     • If heated electrons in an atom release energy as light
       • Wavelengths recorded as a line spectrum
     • Different Elements = different wavelengths
       • because of different electron arrangement
       • Different pattern of wavelengths
         • spectrums used to identify elements
           • Spectroscopy
             • scientist have discovered new elements using this eg, caesium and rubidium.

4. History of the Periodic Table

   • 1800s only measure relative atomic mass, elements aranged in order of this only.
     • Dobereiner
       • Order elements into triads (groups)
         • based on chemical properties
     • Newland
       • Ordered atoms by relative atomic mass, every eigth had similar properties
         • Newlands octives
         • Broke down on 3rd row, he left no gaps, work was ignored.
         • Groups contained elements that didn't have similar properties. Mixed up metals and Non-metals. No Gaps.
     • Mendeleev
       • 1869 arrange 50 known elements, left gaps, predicted unfound
         • keep elements with similar properties in the same vertical groups
         • When the element he left gaps for were discovered people believed his theory more.
       • order of atomic mass

5. The Modern Periodic Table

   • Puts elements with similar properties together.
   • in order of increasing proton number
   • Metals left, none metals right (steps)
   • columns = similar properties
   • groups = vertical column
     • group number tells you how many electrons are on the outer shell
     • if you know properties of one element in the group you can predict the properties of other elements
   • group 1:more reactive as you go down. group 7: less reactive as you go down

6. Electron Shells

   • Rules.
     • electrons occupy shells.
     • lowest energy levels filled first
     • 1st Shell: 2 2nd Shell: 8 3rd Shell:8
     • most outer shells not full
       • makes atom want to react
     • electronic arrangement determines properties
   • Working out Electron Configurations
     • look at the number of protons an atom has.
       • it has the same number of electrons
         • follow shell rules to fill up the shells for the element

7. Ionic Bonding

   • Ions are made when atoms lose or gain electrons
     • can be made from single atoms or groups of atoms.
     • they lose/ gain to try and get a full outer shell
   • Group 1 have 1 electron in outer shell.
     • want to get rid of that one to have full shells.
       • when they lose an electron they form positive ions
   • group 7 have outer shells almost full
     • Want to fill them (get 1 extra electron)
       • when they gain an electron they form negitive ions
   • Ionic compounds form a regular lattice.
     • solid ionic compounds are made of a giant lattice of ions. each lattice forms a single crystal.
       • When they dissolve in water they can conduct electricity because ions can move.

8. Group 1; The Alkali metals

   • 1 outer shell electron
   • Very reactive
     • More violent the reation with water, the more reactive they are.
   • all similar properties
   • When they react they form similar compounds
   • shiny when freshly cut
   • react with oxygen in moist air
   • Down the group
     • more reactive
     • denser
     • lower melting point
     • lower boiling point
   • Produce Hydrogen when reacted with water
     • fizz, some ignite
       • reaction makes an alkaline solution
         • a hoydroxide of the metal forms
   • Reaction with Chlorine makes salts.
     • reacts vigorously, creates colourless crystalline salts.

9. Group 7: Halogens

   • 7 outer electrons
   • very reactive, create similar compounds, have similar properties
   • form diatomic molecules (always in pairs)
   • as you go down the group
     • less reactive
     • higher melting point
     • higher boiling point
   • non-metals with coloured vapours
     • Fl, very reactive poisonous yellow gas @ room temp.
     • Cl, fairly reactive, dense green gas @room temp.
     • Bromine, dense orange volatile liquid @room temperature and forms an orange gas
     • Iodine, dark grey crystaline solid @room temp. or a purple vapour
   • React with alkali metals to form salts
   • They react with iron to form coloured solids called iron halides.
   • Displacement reactions, more reactive element pushes a less reactive element out.

10. Laboratory Safety

    • Hazard Symbols
      • Oxidising
        • Provides oxygen makes other materials burn more fiercely.
      • Explosive
        • Can explode.
      • Highly Flammible
        • Catches fire easily
      • Corrosive
        • attacks and destroys living tissues inc. eyes and skin
      • Toxic
        • Can cause death either by swallowing, breathing in, or absorption through the skin.

Imagens e arquivos do mapa