Period 3

Period 3

1. Sodium is more reactive than Magnesium

   • They're the first two elements in period 3
   • When they react they lose electrons as they're in groups 1 and 2
     • Na loses one electron (Na+)
     • Mg loses two electrons (Mg2+)
   • It takes less energy to remove one electron than two electrons. So more heat is needed for magnesium to react
     • Sodium will react vigorously with cold water
       • 2Na(s)+2H(2)O(l)-> 2NaOH(aq)+H(2)(g)
       • Strong alkaline solution produced
     • Magnesium reacts slowly with cold water, but fast with steam
       • Mg(s) + 2H(2)O(l) -> Mg(OH)(2)(aq) + H(2) (g)
       • MORE ENERGY: Mg(s)+H(2)O (g) -> MgO +H(2)(g)

2. React readily with Oxygen

   • Form oxides usually to their highest oxidation state
   • 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
   • The equations are similar (element + oxygen=> Oxide)
     • 2Na(s) + (1/2)O(2)(g)=> Na(2)O(s)
   • Na, Mg, P, S REACT QUICKLY Na(2)O, MgO, P(4)O(10), SO(2)
     • Al and Si REACT SLOWLY Al(2)O(3), SiO(2)

3. Bonding and structure affect meting points (Oxides)

   • Na, Mg, Al all form giant ionic lattices and so have a high melting point
     • Due to strong forces of attraction between each ion, requires a lot of heat to break the bonds
   • Mg has a higher melting point than Na as it forms 2+ ions which bonds more strongly than Na's 1+ions
   • Al as a lower melting point because the highly charged 3+ ions distort the oxygens electron cloud makig the bonds partially covalent.
   • Si has the highest: giant macromolecular= lots of energy required to break the bonds
   • P and S are the lowest: simple molecular structures: weak Van der Waals and dipole-dipole

4. Ionic oxides

   • Na and Mg both contain O(2-) ions
     • When dissolved in water the O (2-) ions accept H+ ions to for hydroxide ions making it alkaline
       • Na makes it more alkaline than Mg
       • Na(2)O is more soluble in water

5. Covalent oxides

   • P an S form acidic solutions ( PH 0-2) dissociate
     • (split in to ions)
     • E.g. P(4)O(10) s+ 6H(2)O=>4H(3)PO(4) H(3)PO(4)=> 3H+ (aq) + PO(4) 3-
   • Silicon dioxide is insoluble in water because of its structure (macromolecular)
     • However, it still can react with bases to form salts so it is acidic
   • Aluminium oxide is insoluble in water. It is partly ionic and covalent
     • It can act as both an acid and a base so it is amphoteric

6. Acid + base= salt +water

   • Basic oxides neutralise acids
     • Na(2)O (s) + 2HCl => NaCl (aq) +H(2)O (l)
     • MgO(s) + H(2)SO(4) ((aq) => MgSO(4) (aq) + H(2)O
   • Acidic oxides neutralise bases
   • Amphoteric oxides neutralise acids and bases

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