C4 CHEMICAL PATTERNS

C4 CHEMICAL PATTERNS

1. HISTORY OF THE PERIODIC TABLE

   • NEWLANDS
     • noticed the octave pattern, where every 8th element had similar properties, he arranged elements in order of relative atomic mass but mixed up metals and non metals. Criticised as patterns + properties didn't all fit
   • DOBEREINER
     • tried to arrange elements into triads based on chemical properties. Middle element had RAM that was the mean of the other 2
   • MENDELEEV
     • put elements in order of RAM but left gaps for undiscovered + predicted elements so that he could keep elements of the same properties in groups

2. INSIDE ATOMS + ELECTRONS

   • NUCLEUS
     • contains +1 protons, mass of 1, and neutrons mass of 1 too. V strong forces in it to keep positive protons together as they repel each other
   • ELECTRONS- negligible mass, negative charge of 1, in shells around nucleus. For metals: the further the electron is from the nucleus the more reactive the element. For non metals like G7, the further away from the nucleus, the less electrostatic attraction between the nucleus + electrons + the harder it is to attract or gain an electron--> so increase in shells means less reactant
   • electrons in different shells have different energy levels: closer electron to nucleus= lower energy level

3. LINES OF DISCOVERY

   • when elements are heated the emit coloured flames, some elements have a distinctive flame colour. They emit light energy because they gain energy by being heated + the electrons move more. Due to each element having a different electron arrangement, different elements emit different wavelengths+ patterns specific to each element. So spectroscopy + lone spectrums can identify elements e.g. looking @ sun= helium

4. THE PERIODIC TABLE

   • row= period. Group=electron number in outer shell. Left--> right: metals-->non-metals + increase in RAM + proton number. Properties change across rows + periods = trend. Atoms <3 elements in outer shell=metals 5+=non-metals

5. GROUP 1- THE ALKALI METALS

   • are the alkali metals. They all have 1 electron in their outer shell so are very reactive. The reactivity of G1 show a trend down the group as it increases because the electron shell number increases and theres less electrostatic force keeping the electron near the nucleus so its easier to remove and react. MP + BP decrease.
   • appearance at room temperature- all soft meals that can be cut with a knife, freshly cut they are shiny but they soon react with the moist air and tarnish.
   • they all form ions with a +1 charge as they lose their outer electron
   • Li, Na, K, Rb, Cs, Fr
     • flammable, corrosive, gloves, glasses.
   • Reactions with water- all G1 elements react vigorously with water. They fizz + move around the surface, but K + Rb explode within contact. The reaction makes a metal hydroxide so pH indicator turn blue. Metal + Water--> Metal Hydroxide + Hydrogen
   • Reactions with chlorine- sodium reacts vigorously to give yellow flame + white solid. Reaction rate increases down the group and ionic compounds of metal+ halogen--> metal halides

6. GROUP 7- THE HALOGENS

   • Appearance at room temperature- Chlorine= pale green gas, Bromine= red,brown liquid (red/brown gas) + Iodine= dark grey solid (purple gas)
   • they are all diatomic so have 2 atoms joined together for each molecule
     • Reactions with Iron- fluorine most reactive, iodine only reacts when heated + all form coloured halide.
   • trends down the group -reactivity decreases because electrons are further away from nucleus so weaker electrostatic attraction so harder to gain electron/ react., MP + BP increases
   • G7 react with G1 to form metal halides: alkali metal+halogen-->metal halide
   • Displacement Reactions- when a more reactive halogen takes the place of a less reactive one. Chlorine= more reactive than Bromine so it displaces Bromine in a Potassium Bromide solution.

7. IONIC COMPOUNDS

   • compounds of G1+G7 have high melting points and are ionic compounds because they contain charged particles called ions that are arranged in a regular pattern called a crystal lattice. Ionic compounds are soluble in water + conduct electricity when molten or in water as the electrons are free to move to complete the circuit.G1 lose an electron--> positive ion. G7 gain an electron-->negative ion. The ions have the same electron arrangement then as inert gases of G0.