Periodic Trends in Period 3

Chlorides and Oxides

Bonding and Structure

•Position of elements on the periodic table affects the type of bonding.

Period 3: ChloridesPeriod 3: Chlorides•NaCl, MgCl2, AlCl3, SiCl4, PCl5

– increase in the number of electrons available to form bonds.

increasing valence e-

•Chlorides of Metals (NaCl, MgCl2)– ionic– high melting points– soluble in water– do not react with water– electrolytes (conduct electricity) as

aqueous solutions or molten (liquid)– NaCl(aq) Na+(aq) + Cl-(aq)

Electrolyte

•Chlorides of Non-Metals (PCl5, PCl3)– molecular/covalent– weak van der Waal’s forces between

molecules = low melting and boiling points

– hydrolysis: to split by the action of water

PCl3(l) + 3H2O(l) P(OH)3(aq) + 3H+(aq) + 3Cl-(aq)

– non-metal/Cl bond replaced by a non-metal/O bond

– non-metal chlorides (aq) conduct electricity (but not when molten)

– Cl2: molecular/covalent, reacts with water in a hydrolysis reaction

Cl2(g) + H2O(l) HOCl(aq) + HCl(aq) – Al: metal, but acts like a non-metal in bonds

•because of it’s high charge, small size ion

Period 3 Oxides• Na2O, MgO, Al2O3, SiO2, P4O10, SO3, Cl2O7

• P4O6 SO2 Cl2O basic acidic

•reducers oxidizers•(donate e-) (accept e-)

•Metals: Na, Mg– ionic solids–basic– react with water to make alkaline

solutionNa2O(s) + H2O(l) 2Na+(aq) + 2OH-(aq)

•Metalloids: Al–“giant covalent lattices”–high melting/boiling points– insoluble in water– Al2O3 is amphoteric (dissolves in acid or

base)

– Al2O3(s) + 6H+(aq) 2Al3+(aq) + 3H2O(l)

– Al2O3(s) + 2OH-(aq) 3H2O(l) + 2Al(OH)4(aq)

•Non-metals: Si, P, S, Cl– molecular/covalent bonding– gases, liquids, solids with low melti

ng points– non-metal oxides react with water t

o produce acids P4O10(s) + 6H2O(l) 4H2PO4-(aq) + 4H+(aq)

Element Na Mg Al Si P S Cl

BondingMetallic

　　 Giant Covalent Lattice

　Molecular/ Covalent

　　 　 　 　 　 　 　 　Chloride 　 　 　 　 　 　 　Formula NaCl MgCl2 AlCl3 SiCl4 PCl5/PCl3 　 Cl2

Bonding Ionic 　 Molecular/covalent

　 　 　 　 　 　 　 　Oxide 　 　 　 　 　 　 　Formula Na2O MgO Al2O3 SiO2 P4O10 SO3 Cl2O7

　 　 　 　 　 P4O6 SO2 Cl2O

Bonding Ionic Giant Covalent Molecular/Covalent

　 　 　 　 　 　 　 　

Acid/Base Soluble Insoluble AmphotericInsoluble

　Soluble

　acidic

　Properties basic basic 　 acidic