Transcript Periodic Trends

Periodic Trends
3.3 Chemical properties
3.3.1
Discuss the similarities and differences in the chemical properties of elements in
the same group.
The following reactions should be covered:
Alkali metals (Li, Na and K) with water
Alkali metals (Li, Na and K) with halogens (Cl2, Br2 and I2)
Halogens (Cl2, Br2 and I2) with halide ions (Cl–, Br– and I–)
3.3.2
Discuss the changes in nature, from ionic to covalent and from basic to acidic, of
the oxides across period 3.
Equations are required for the reactions of Na2O, MgO, P4O10 and
SO3 with water.
Periodic Trends
Alkali metals (Li, Na and K) react with water
Li(s) + H2O(l)  LiOH (aq) + H2(g) + heat
**these reactions produce metal hydroxides which are basic.
Na(s) + H2O(l)  NaOH (aq) + H2(g) + HEAT
*the amount of hydrogen along with the amount of heat can lead to the
ignition of the hydrogen.
K(s) + H2O(l)  KOH (aq) + H2(g) + a LOT of HEAT
*the amount of hydrogen along with the amount of heat does lead to the
ignition of the hydrogen.
Periodic Trends
Alkali metals (Li, Na and K) with halogens (Cl2, Br2 and I2)
(metal with non-metal)
2 Li(s) + Cl2(g) (+ heat)  2 LiCl(s) + HEAT (somewhat vigorous)
*note: you have to put some energy in to START the reaction (think of striking a match)
2 Na(s) + Cl2(g) (+ heat)  2 NaCl(s) + LOT of HEAT (vigorous)
(why would this reaction give off more heat and be more vigorous?)
2 K(s) + Cl2(g) (+ heat)  2 KCl(s) + LOT of HEAT (very vigorous)
Periodic Trends
Halogens (Cl2, Br2 and I2) with halide ions (Cl–, Br– and I–)
(Displacement reactions)
2 KBr(aq) + Cl2 (g)  2 KCl (aq) + Br2(aq) (red color)
or
2 Br-(aq) + Cl2 (g)  2 Cl-(aq) + Br2(aq) (red color)
**The more reactive halogen displaces the ions of the less reactive halogen.
(??How do we know which is more REACTIVE?!?!?)
2 Br-(aq) + I2 (g)  No Reaction
What about:
(why?)
2 F-(aq) + Br2 (g) ???
Nope: But F2(g) + 2 Br-(aq)  2 F-(aq) + Br2(aq)
Properties of the Third Period Oxides
Formula
Na2O
MgO
Al2O3
SiO2
P4O10
(P4O6)
SO3
(SO2)
Cl2O7
(Cl2O)
State
(@ 25 oC)
Solid
Solid
Solid
Solid
Solid
Liquid
(gas)
Gas
MP oC
1275
2852
2027
1610
24
17
-92
Structure

Ionic

Covalent
Network

Covale
nt

Electrical
Conductivity
Good
Good
Good
Very Poor
None
None
None
Nature of
Oxide
Basic
Basic
Amphoteric
Amphoteric
Acidic
Acidic
Acidic
.5
Properties of the Third Period Oxides
• Na2O + H2O  2 NaOH
•
(sodium hydroxide – base)
• MgO + H2O  Mg(OH)2
•
(magnesium hydroxide)
• P4O10 + H2O  H3PO4
•
(phosphoric acid)
• SO3 + H2O  H2SO4
•
(sulfuric acid)
.6
Alternate Periodic Tables
.7
Alternate Periodic Tables II
.8
Alternate Periodic Tables III
.9
Alternate Periodic Tables IV