Periodicity

• s block


  The block that belongs to hydrogen and groups 1 and 2Elements that have their highest energy e- in s-orbitalsE.G. Na 1s1 2s2 2p6 3s1

  
• p


  The block that belongs to the non-metals and metalloidsElements that have their highest energy e- in p-orbitalsE.G. C 1s1 2s2 2p2

  
• d

  Transition metals and b-block are not exactly the same (Scandium and Zinc are not transition metals)Elements that have their highest energy e- in d-orbitals1s1 2s2 2p6 3s2 3p6 4s2 3d6
• f


  The block that belongs to the lanthanides and antinides
• Groups

  columns on the periodic tableElements have similar properties in same group1-8 or 1-18 (if transition included)
• Reactivity


  s-block elements (metals) are more reactive going down a group (increased shielding counteracts increased nuclear chanrgenon-metals are more reactive going up a groupTransition metals are rather unreactive
• Structure and bonding of period 3 elements


  Group 1, 2, 3 (Na, Mg, Al): giant metallic, lose outer e- to form ionic compoundsGroup 4 (Si): 4 outer e- forming 4 covalent bonds (macromolecular), some metallic propertiesGroup 5, 6, 7 (P, S, Cl): non-metals, either accept e- to form ionic compounds or share outer e- to form covalent bonds (molecular)Group 0/8: unreactive
• Trend in BP/MP across period 3


  Na to Al increases due to metallic structure (more e- in sea so stronger attraction)Si semi-metallic and forms macromolecular bonds (very strong) depends on vdWP to Cl are simple molecular (force increases in correlation to size) S8 > P4 > Cl2

  
• Atomic radius


  - one-half the distance between the nuclei of identical atoms that are bonded together- periodic property as it decreases across a period and a jump up at the start of another period

  
• The trend in atomic radii across a period

  DecreaseNumber of protons in nucleus increases across period but e- in same shell (nuclear charge increases)Electrostatic attraction causes shells to be closer together
• The trend in atomic radii down a group

  IncreaseDown the group, an energy level is added therefore the outermost e- is further away and attraction is weaker
• The trend in first ionisation energy across a period

  Increase (stronger attraction as more protons, nuclear charge)More energy to remove as greater attraction (same shell)
• The trend in first ionisation energy down a group

  Increase in shieldinge- is further away so requires less energy to be removed
• Drop in IE between: groups 2 and 3, groups 5 and 6


  Decrease between Mg and Al as Al is in p sub-level which is in a higher energy than S (Al removes e- easier)Ph and S, S has two e- in same orbital so needs less energy to remove due to repulsion
• Why is their a drop in IE from one period to another

  Ne 2, 8 and Na 2, 8, 1 sharp dropNa is at a new main level so there is an increase in atomic radiusOuter e- is further from nucleus, less strongly attracted and easier to remove
• Successive Ionisation Energies


  A measure of the energy needed to remove each electron in turn until all the electrons are removed from an atom