Module 3 - Periodic table and energy

• Le Chatilier's principle:

  in dynamic equilibrium if there is a change in conditions, equilibrium shifts to counteract the change
• Equilibrium: increase of concentration of reactants

  • equilibrium shifts right
  • increases forward reaction
  • decreasing reactants and increasing products
• Equilibrium: decrease of concentration of reactants

  • equilibrium shifts left
  • increasing the reverse reaction
  • increasing reactants and decreasing products
• Equilibrium: decrease in concentration of products

  • equilibrium shifts right
  • increase forward reaction
  • increasing products and decreasing reactants
• Equilibrium: increase of concentration of products

  • equilibrium shifts left
  • increasing reversed reaction
  • decreasing products and increasing reactants
• Equilibrium: increase in temperature

  • equilibrium shifts to reduce the temperature
  • favours endothermic reaction
• Equilibrium: decrease in temperature

  • equilibrium shifts to increase the temperature
  • favours exothermic reaction
• Equilibrium: increase in pressure

  • equilibrium shifts to favour less gas mole
• Equilibrium: decrease in pressure

  • equilibrium shifts to favour more gas mole
• Equilibrium: catalysts

  • catalysts have no effect on equilibrium as both forward and reverse reactions are increased equally
• mendeleev's periodic table:

  • 60 known elements
  • arranged in atomic mass
  • left gaps for undiscovered elements
• today's periodic table:

  • arranged in atomic number
  • groups - vertical columns
  • periods - horizontal vows
• electron configuration:

  • same-grouped elements have the same no of electrons in the outer shell
  • same grouped elements have the same no of electrons in sub-shells
• ionisation energy:

  • the ability to lose an electron from an atom to form a positive ion
• first ionisation energy:

  • the energy required to remove 1 electron in each atom from 1 mole of gaseous atoms to form 1 mole of 1+ gaseous ions
• factors affecting ionisation energies:

  • nuclear charge - more protons more attraction
  • atomic radius - closer distance more attraction
  • electron shielding - less shells more attraction
• successive ionisation energies

  • depends on electrons in the outer shell
  • once outer shell in removed ionisation energy increases
  • due to less shielding and small atomic radius
• trends in ionisation energies - N to O drop

  • in oxygen in the p-orbital electrons start to pair up so due to repulsion its easier to remove 1 electron
• trends in ionisation energy: Be to B drop

  • boron has a p-orbital while beryllium doesn't, so boron has a higher energy so it is easier to remove
• metallic bonding:

  • strong electrostatic attraction between cation and delocalised electrons due to opposite poles
  • is a giant metallic lattice structure
• metallic bonding properties

  • conductivity - in solids and liquids delocalised electron carry charge
  • points - high as lots of energy needed to overcome electrostatic attractions
  • solubility - doesn't dissolve as a reaction will take place no dissolving
• giant covalent bonding:

  • simple molecular lattice - N, O, S, P, F, Cl - weak London forces
  • giant covalent lattice - C, B, Si - strong covalent bonds
• Diamond + Silicon conductivity

  • all 4 electrons are bonded to the carbon so there are no delocalised electrons to carry charge

  Graphite conductivity

  • only 3 are bonded to carbon so 1 delocalised electron to carry charge
• Group 2:

  • metals are very reactive and do not occur in elemental from so naturally found in stable compounds
• Group 2 REDOX reactions:

  • metal + oxygen = metal oxide
  • metal + water = metal hydroxide + hydrogen
  • metal + acid = salt + hydrogen
• Group 2 trends:

  • reactivity increases - more shielding and a larger atomic radius
  • solubility of hydroxides increases - due to more hydroxide ions
• group 2 uses:

  • bases - can neutralise acids
  • agriculture - calcium hydroxide increases soil pH to neutralise acid in soil to produce water
  • medicine - magnesium and calcium tablets treat acid indigestion
• Halogens:

  • non-metals which are very reactive and do not occur in their elemental form
• Group 7 reactions:

  • redox - oxidising agents as it causes other species to lose electrons
  • displacement - non-metals displace each other depending on halide reactivity
• Group 7 trends:

  • boiling point increases - more electrons, more London forces more energy required to break
  • reactivity decreases - large atomic radius, more shielding and less nuclear attraction
• colour analysis on group 7s in water

  • chlorine - pale green
  • bromine - orange
  • iodine - brown
• colour analysis on group 7s in cyclohexane

  • chlorine - pale green later
  • bromine - orange layer
  • iodine - violet layer
• qualitative analysis: carbonate test

  • add nitric acid - bubbles formed
  • test if CO2 run through lime water to from white precipitate
• qualitative analysis: sulfate test

  • add barium nitrate - white precipitate forms
• qualitative analysis: halide test

  • add silver nitrate

  chlorine - white, bromine - cream, iodine - yellow

  • to see clear results add ammonia
• in qualitative analysis: the order

  • carbonate
  • sulfate
  • halide
  • ammonium
• qualitative analysis: ammonium test

  • add sodium hydroxide
  • add damp red litmus paper - turns blue
• in qualitative analysis: why this order

  • carbonate - sulfate or halides don't produce bubbles
  • sulfate - carbonates will form a white precipitate
  • halide - carbonates and sulfates will from precipitates
• enthalpy - the measure of heat lost and gained in a chemical reaction
• enthalpy change equation:

  • H(products) - H(reactants)