C4 - Chemical Patterns

C4 - Chemical Patterns

1. The Atom

   • The Nucleus
     • it is in the middle of the atom and is positively charge
     • Contains Protons
       • Protons are particles with a mass of 1 and a charge of +1
     • Contains Neutrons
       • Neutrons are particles with a mass of 1 and a charge of 0
   • The Electrons
     • Electrons move around the shells of an atom
     • they have a mass of 0.0005 and a charge of -1

2. Line Spectrums

   • Spectroscopy
     • When attoms are heatd they give off energy as light the wavelengths emmited can be recored as a line spectrum
     • Different elements emit different wavelenths of light this can be used to identify new elements
   • Flame testing
     • When attoms are heated they give off a specific colour this can be used to identify elements

3. History of the periodic table

   • Dobereiner
     • Dobereiner put elements into groups of three triads eg Cl Br and I where one group and Li Na and K were another
     • He worked out that the middle element of each group had a relative atomic mass that was the average of the other two
   • Newland
     • Newland noticed that when you arranged the elements in order of relative atomic mass every eighth element had similar properties
     • Newlands work was criticised
       • His groups contained elements that didnt have similar properties eg carbon and titanium
       • He mixed metals and non metals eg oxygen and iron
       • He didn't leave gaps for element that haven't been discovered yet
   • Dmitri Mendelleev
     • He put elements in order of atomic mass but left gaps for elements that hadn't been discovered yet
     • The gaps predicted properties of undiscovered elements and whern they fitted his patten it confirmed Medeleevs ideas

4. The Modern Periodic tabel

   • atoms in the same period have the same number of shells
   • All atoms in the same group have the same number of electrons of their outer shell
   • As you go down the group an extra shell is needed
   • across the periods an extra proton and electron is added

5. Ionic Bonding

   • When atoms lose or gain electrons they form charged particles called ions
   • Atoms bond so they can gain a full outer shell of electrons and become stabel
   • Ionic bonds form between metals and non metals metal lose electrons and become +ve and non metals gain electrons becoming -ve
   • The atoms become oppositely charged ions which have a strong electrostatic attraction to each other

6. Alkali Metals

   • Down the group
     • They become more reactive because their outer electron is further from the nucleus
     • Higher density
     • Lower melting and boiling point
   • reaction with water
     • They react with water to form metal hydroxide and hydrogen
     • lithium + water → lithium hydroxide + hydrogen 2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
   • Shiny when cut but react with oxygen in the air to become dull

7. The Hallogens

   • Down the groups
     • They become less reactive as their outer electrons are further from the nucleus
     • Have a higher Melting and Boiling point
   • Reaction with alkali metals
     • React with Alkali metals to produce a salt
   • Displacement reactions
     • The more reactive hallogen displaces the less reactive one
     • chlorine + sodium bromide → sodium chloride + bromine Cl2 + 2NaBr → 2NaCl + Br2
   • The halogens all exist as diatomic molecules, two halogen atoms joined together by a covalent bond eg Cl2