Periodicity
Topic 13
CH 7 p. 255-287
CH 24 p. 1013-1014
Oxford p. 15-16
Syllabus p. 71-72
Third Period (NaAr)
• Metallic character
• Na, Mg, Al
– Metals
– all conduct electricity well
• Si
– Metalloid
– Semi-conductor
• P, S, Cl, Ar
– Non-metals
– Do not conduct electricity well
Third Period (NaAr)
• Oxides
• Na2O, MgO, Al2O3 *
– Ionic
– High melting/boiling points
– Conduct electricity when molten (or
aqueous solution)
• SiO2
– Diamond-like macromolecule
– High melting/boiling point
• P4O10, SO3, Cl2O7
–
–
–
–
Covalent molecules
Molecules attracted by Van der Waals forces
Low melting/boiling points
Don’t conduct electricity in molten state (or aqueous)
Acid/Base Nature of the Oxides of the
Third Period (NaAr)
•
Na2O, MgO
– Very basic, form alkaline solutions
– Na2O (s) + H2O (l)  2NaOH (aq)
– MgO (s) + H2O (l)  Mg(OH) 2 (aq/s)
•
Al2O3
– Amphoteric, can be acidic or basic
– Al2O3 (s) + 6HCl (aq)  2AlCl3 (aq) + 3H2O (l)
– Al2O3 (s) + 2NaOH(aq)  3H2O (l) + 2NaAl(OH)4 (aq)
•
SiO2
– Weak acid
– SiO2 (s) + 2NaOH(aq)  Na2 SiO3 (aq) + H2 O (l)
•
“sodium aluminate”
“sodium silicate”
P4O10, SO2, Cl2O7
– Strongly acidic
– P4O10 (s) + 6 H2O (l)  4H3PO4 (aq)
– SO2 (g) + H2O (l)  H2SO3 (aq)
– Cl2O7 (l) + H2O (l)  2HClO4 (aq)
phosphoric acid
sulfurous acid
perchloric acid
Chlorides of the Third Period (NaAr)
•
NaCl, MgCl2
– Ionic
– High melting/boiling points
– Reactions with water
• NaCl (aq)  Na+ (aq) + Cl- (aq)
• MgCl2 (aq)  Mg2+ (aq) + 2Cl- (aq)
Neutral solution
Slightly acidic solution
•
AlCl3,
– Covalent molecule
– Poor conductor
– Reacts vigorously with water to give acidic solutions of hydrochloric acid as well as hydrochloric acid
fumes
• 2AlCl3 (s) + 3H2O (l)  Al2O3 (s) + 6HCl (aq)
•
SiCl4, PCl3 , S2Cl2
–
–
–
–
•
Cl2
–
–
Simple molecular structure
Molecules held together by weak van der Waal’s forces
Low melting/boiling points
Reacts vigorously with water to give acidic solutions of hydrochloric acid as well as hydrochloric acid
fumes
• SiCl4 (l) + 4H2O (l)  Si(OH)4 (aq) + 4HCl (aq)
• PCl 3 (l) + 3H2O (l)  H3PO3 aq) + 3HCl (aq)
Reacts somewhat with water to form an acidic solution
Cl2(aq) + H2O (l)  HCl (aq) + HClO (aq) hypochlorous acid
Conductivity of Chlorides?
• Ionic (metals)
– Conduct in molten and aqueous states
– Both = motile ions
• Molecular Covalent (nonmetal chlorides)
– Do not conduct in molten state
– Conduct in aqueous solutions
Bookwork
• Alternative Text Ch. 3
– Pg. 84
#3, 4, 5