periodicity

• which side of the periodic table in period 3 generally have higher MP and BP?

  left
• what is the trend in MP and BP in period 3?

  decreases as you go across, metals increase across though due to stronger metallic bonds because ion charge increases
• what element has the highest MP and BP in period 3?

  silicon because it has ma macromolecular structure so has very strong covalent bonds
• what is the definition for first ionisation energy?

  the amount of energy needed to remove the most loosely bound electron from 1 mole of gaseous atoms to produce 1 mole of gaseous ions with a charge of +1
• what are the trends in first ionisation energy in period 3?

  increase across due to more protons and increased nuclear charge creating great forces of attraction, decrease down due to a bigger distance between nucleus and electrons due to new energy level, weaker forces of attraction
• what are the anomalies in first ionisation energy in period 3?

  drop between 2&3 due to a new sub-shell causing a bigger distance and more shielding, drop between 5&6 because an electron pair is completed they repel each other (bus analogy)
• what is successive ionisation energy?

  energy needed to remove one electron after another, energies increase after each electron due to them being closer to the nucleus
• where is atomic radii measured from?

  half the distance between the centers of a pair of atoms
• why can you not measure a radius from an isolated atom?

  no clear point where electron cloud density drops to 0, atom radii of elements differ due to different bonding
• what are the trends in atomic radii in period 3?

  increases going down due to more shells and larger atoms, decreases going across due to more protons and a bigger nuclear charge
• what are the trends in melting points in group 2?

  decreases as you go down, because bonds get weaker and there is a lower charge density so weaker attraction forces occur between delocalised electrons and ion
• what are the trends in ionic radii in group 2?

  increase as you go down, more shells of electrons so bigger radius
• what is the trend in ionisation energies in group 2?

  decrease as you go down because outer electrons are further from the nucleus and there is more shielding, this means the electrostatic forces are smaller and easier to remove out electrons
• what is the trend in group 2 hydroxides solubilities?

  they increase in solubility in water as you go down
• what is the trend in group 2 sulfates?

  decrease in solubility as you go down
• what is barium sulfate used for?

  swallowed to outline a patients gut in x-rays, it is safe as its so insoluble it cannot be absorbed so it not harmful
• what happens when a group 2 metals when they react with water?

  they react with cold water to form a metal hydroxide and hydrogen, they get more reactive as you go down, these are redox reactions
• does magnesium react with water?

  it reacts very slowly with cold water but very fast with steam to form alkaline oxide and hydrogen
• what happens when calcium reacts with water?

  reacts fairly slowly with cold water but very vigorously with steam
• what happen when stronium and barium react with water?

  same as magnesium and calcium but just more vigorously
• what do group 2 metals always from in redox reactions?

  they are always oxidised, they lose electrons and go from oxidation state 0 to +2
• what are the halogens and what are there common trends?

  group 7 elements, all non-metals and appear as diatomic molecules (Cl2), they get darker and denser as you go down and reactivity decreases as you go down
• what state are group 7 elements at room temp?

  fluorine and chlorine are gases, bromine is liquid and iodine is solid
• what are the trends in size of atom in group 7?

  as you go down it increases due to an extra shell of electrons
• what are the trends in electronegativity in group 7?

  as you go down electronegativity decreases, this is because the shared electrons get further away from the nucleus which increases shielding and nuclear charge which all decreases electronegativity
• what are the trends in MP and BP in group 7?

  they increase as you go down, the bigger the atom the more electrons there are, this makes the Van Der Waal forces bigger and harder to break
• what is chlorine and what are its main uses?

  reacts with water in a reversible reaction, used in swimming pool to kill bacteria, just a little is used so its dangerous, benefits to health of water treatment outweigh toxic effects of chlorine
• what is the oxidising agent of chlorine?

  CLO-
• what is a reaction called when something gets oxidised and reduced?

  disproportionation reaction
• what is the disproportionation reaction for chlorine?

  $Cl_2(g)+$$H_2O(l)\Leftrightarrow HClO(aq)+$$HCl(aq)$
• what is the equation for chlorine in sunlight?


  happens in the presence of light, pools need to replenish chlorine

  
• what happens in a reaction between sodium chloride and water?

  to stop the equilibrium shifting to the left you add acid

  
• what happens when chlorine reacts with an alkali?

  NaCLO is an oxidising agent and is bleach

  
• what is the trend with reducing power in halide ions?

  increases as you go down
• how do you test for a halide ion?

  1. add acidified silver nitrate (not HCl as it ruins test)
  2. add ammonia (dilute then conc)
• what are the results when testing for a halide ion?

  fluorine - no ppt

  chlorine - white ppt, redissolves in ammonia

  bromine - cream ppt, redissolves in conc ammonia

  iodine - yellow ppt, never redissolves
• why do we acidify when testing for halide ions?

  to get rid of any carbonates
• what happens in a displacement reaction in halide ions?

  halogens react with metal halides in displacement reactions where the less reactive halogen will get displaced by the more reactive one