Period 3

Sodium is more reactive than Magnesium
1. They're the first two elements in period 3
2. When they react they lose electrons as they're in groups 1 and 2
  1. Na loses one electron (Na+)
  2. Mg loses two electrons (Mg2+)
3. It takes less energy to remove one electron than two electrons. So more heat is needed for magnesium to react
  1. Sodium will react vigorously with cold water
    1. 2Na(s)+2H(2)O(l)-> 2NaOH(aq)+H(2)(g)
    2. Strong alkaline solution produced
  2. Magnesium reacts slowly with cold water, but fast with steam
    1. Mg(s) + 2H(2)O(l) -> Mg(OH)(2)(aq) + H(2) (g)
    2. MORE ENERGY: Mg(s)+H(2)O (g) -> MgO +H(2)(g)
React readily with Oxygen
1. Form oxides usually to their highest oxidation state
2. Sulphur is an exception it produces SO(2) which has a +4 oxidation state. If a high temperature and a catyst is present then SO(3) can be produced ith an oxidation state of +6
3. The equations are similar (element + oxygen=> Oxide)
  1. 2Na(s) + (1/2)O(2)(g)=> Na(2)O(s)
4. Na, Mg, P, S REACT QUICKLY Na(2)O, MgO, P(4)O(10), SO(2)
  1. Al and Si REACT SLOWLY Al(2)O(3), SiO(2)
Bonding and structure affect meting points (Oxides)
1. Na, Mg, Al all form giant ionic lattices and so have a high melting point
  1. Due to strong forces of attraction between each ion, requires a lot of heat to break the bonds
2. Mg has a higher melting point than Na as it forms 2+ ions which bonds more strongly than Na's 1+ions
3. Al as a lower melting point because the highly charged 3+ ions distort the oxygens electron cloud makig the bonds partially covalent.
4. Si has the highest: giant macromolecular= lots of energy required to break the bonds
5. P and S are the lowest: simple molecular structures: weak Van der Waals and dipole-dipole
Ionic oxides
1. Na and Mg both contain O(2-) ions
  1. When dissolved in water the O (2-) ions accept H+ ions to for hydroxide ions making it alkaline
    1. Na makes it more alkaline than Mg
    2. Na(2)O is more soluble in water
Covalent oxides
1. P an S form acidic solutions ( PH 0-2) dissociate
  1. (split in to ions)
  2. E.g. P(4)O(10) s+ 6H(2)O=>4H(3)PO(4) H(3)PO(4)=> 3H+ (aq) + PO(4) 3-
2. Silicon dioxide is insoluble in water because of its structure (macromolecular)
  1. However, it still can react with bases to form salts so it is acidic
3. Aluminium oxide is insoluble in water. It is partly ionic and covalent
  1. It can act as both an acid and a base so it is amphoteric
Acid + base= salt +water
1. Basic oxides neutralise acids
  1. Na(2)O (s) + 2HCl => NaCl (aq) +H(2)O (l)
  2. MgO(s) + H(2)SO(4) ((aq) => MgSO(4) (aq) + H(2)O
2. Acidic oxides neutralise bases
3. Amphoteric oxides neutralise acids and bases

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Period 3

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