1. METALLIC AND NON-METALLIC OXIDES

2. OXIDES OF PERIOD 3 ELEMENTS
SUMMARY
Na2O MgO Al2O SiO SO2
Melting
point / K
bonding ionic ionic ionic/cov covalent covalent
structure giant giant giant giant simple
lattice lattice lattice molecular molecular
classification basic basic amphoteric acidic acidic
solubility very sparingly insoluble insoluble reacts
in water
solution pH

3. OXIDES OF PERIOD 3 ELEMENTS
PREPARATION
• metals produce basic oxides
• non-metals produce acidic oxides
• aluminium oxide is an amphoteric oxide (acidic and basic properties)
• ionic oxides have high melting points
• ionic oxides conduct electricity when molten
• most oxides can be prepared by direct combination (EXC. SO3)
2Mg(s) O2(g) ——> 2MgO(s)
4Al(s) O2(g) ——> 2Al2O3(s)
S(s) O2(g) ——> SO2(g)
+2 -2
+3 -2
+4 -2

4. OXIDES OF PERIOD 3 ELEMENTS
PROPERTIES
Na2O • white solid
• giant ionic lattice
• soluble in water to form a strongly alkaline solution (pH = 13-14)
Na2O(s) + H2O(l) ——> 2NaOH(aq)
• reacts with acids to form salts – A BASIC OXIDE
Na2O(s) + HCl(aq) ——> NaCl(aq) H2O(l) Na + O 2- Na +

5. OXIDES OF PERIOD 3 ELEMENTS
PROPERTIES
MgO • white solid
• giant ionic lattice
• sparingly soluble in water to form hydroxide (pH = 9)
(Low solubility is due to metal’s greater charge density)
MgO(s) + H2O(l) ——> Mg(OH)2(aq)
• reacts with acids to form salts – A BASIC OXIDE
MgO(s) + 2HCl(aq) ——> MgCl2(aq) H2O(l) Mg 2+ O 2-

6. OXIDES OF PERIOD 3 ELEMENTS
PROPERTIES
Al2O3 • giant lattice with some covalent character
• insoluble in water
• AMPHOTERIC; it reacts with both acids and alkalis to give salts
with acids Al2O3(s) + 6HCl(aq) ——> 2AlCl3(aq) H2O(l)
with alkalis Al2O3(s) + 2NaOH(aq) + 3H2O(l) ——> 2NaAl(OH)4(aq)
There is no need to learn these equations

7. OXIDES OF PERIOD 3 ELEMENTS
PROPERTIES
SO2 • simple covalent molecule
• soluble in water
• reacts with water to give a weak acidic solution (pH = 3)
SO2(g) H2O(l) H+(aq) + SO32-(aq) O S
ANGULAR / BENT
There is no need to learn this equation

8. OXIDES OF PERIOD 3 ELEMENTS
PROPERTIES
SO3 • simple covalent molecule
• reacts violently with water to give a strong acidic solution (pH = 0) O S
TRIGONAL PLANAR