1. Periodic Trends in Chemical Properties
Chapter 3 – Green/Damji
Chapter 8 - Chang
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2. 2M(s) + 2H2O(l) 2MOH(aq) + H2(g)
Group 1 Elements (ns1, n  2)
(Alkali) Metals are electron donors, they form cations
M M+1 + 1e-
Write the corresponding equation for sodium:
(Alkali) Metals react with water to form hydroxides – which are bases.
2M(s) + 2H2O(l) MOH(aq) + H2(g)
8.6

3. Group 1 Elements 2M(s) + 2H2O(l) 2MOH(aq) + H2(g)
2 Li(s) + 2 H2O(l) __________(aq) + H2(g)
slow and steady
2 Na(s) + 2 H2O(l) ___________(aq) + H2(g)
vigorous
2 K(s) + 2 H2O(l) KOH(aq) + __________
violent
Increasing reactivity
8.6

4. Group 1 Elements (ns1, n  2) 4M(s) + O2(g) 2M2O(s)
(Alkali Metals react with oxygen to form metal oxides
4M(s) + O2(g) M2O(s)
Write the corresponding equation for sodium:
(Alkali) Metals react with halogens to form metal halides (salts)
2 M(s) + X2(g) MX(s)
Write the corresponding equation for sodium:
8.6

5. Group 2 Elements (ns2, n  2) M M+2 + 2e-
M(s) + 2H2O(l) M(OH)2(aq) + H2(g) M = Mg, Ca, Sr, or Ba
Be(s) + 2H2O(l) No Reaction
Mg(s) + 2H2O(g) Mg(OH)2(aq) + H2(g)
Increasing reactivity
8.6

6. Group 3 Elements (ns2np1, n  2)
4Al(s) + 3O2(g) Al2O3(s)
2Al(s) + 6H+(aq) Al3+(aq) + 3H2(g)
8.6

7. Group 4 Elements (ns2np2, n  2)
Sn(s) + 2H+(aq) Sn2+(aq) + H2 (g)
Pb(s) + 2H+(aq) Pb2+(aq) + H2 (g)
8.6

8. Group 5 Elements (ns2np3, n  2)
N2O5(s) + H2O(l) HNO3(aq)
P4O10(s) + 6H2O(l) H3PO4(aq)
8.6

9. Group 6 Elements (ns2np4, n  2)
SO3(g) + H2O(l) H2SO4(aq)
8.6

10. Group 7 Elements (ns2np5, n  2)
Halogens are electron acceptors, form anions
X2 + 2e X-1
Write the corresponding equation for chlorine:
Halogens react with hydrogen to form hydrogen halides (which are acids )
X2(g) + H2(g) HX(g)
Write the corresponding equation for bromine:
8.6

11. Group 7 Elements (ns2np5, n  2)
Halogens react with water to form acids )
X2(g) + H2O(g) HX(aq) + HOX (aq)
Write the corresponding equation for chlorine:
[Note: HCl is hydrochloric acid, a strong acid and HOCl (aq) is chloric acid, a weak acid ]
8.6

12. Group 7 Elements (ns2np5, n  2)
Metals react with halogens to form metallic halides…
The level of reactivity depends on the trends of reactivity for both the metal and the halogen…
Increasing reactivity
Increasing reactivity
8.6

13. Reactivity of Metals with Halogens
Ex: Which of the following pairs of chemicals will react most vigorously? Least vigorously?
K and Br2 Li and I2 Na and I2
Na and F2 K and F2 Li and Br2
2 M(s) + X2(g) MX(s)
Write the corresponding equations:

14. Reactivity of Halogens with Halides
2 M+X-(aq) + X2(aq) M+X-(aq) + X2 (aq)
F2 (aq) + 2 Na+Cl-(aq) Na+F-(aq) + Cl2 (aq)
F2 (aq) + 2 Na+Br-(aq) Na+F-(aq) + Br2 (aq)
F2 (aq) + 2 Na+I-(aq) Na+F-(aq) + I2 (aq)
Cl2 (aq) Na+Br-(aq) Na+Cl-(aq) + Br2 (aq)
Cl2 (aq) Na+I-(aq) Na+Cl-(aq) + I2 (aq)
Br2 (aq) Na+I-(aq) Na+Br-(aq) + I2 (aq)
Compare the reactions/reactivity with the position of the halogen / halide on the periodic table? What is the pattern?

15. Identifying halide ions
The presence of halide ions can be detected by reacting the salt with lead or silver salts… and observing the resulting precipitates. They have characteristic colors. (You did this in lab )
Ag+(aq) X(aq) AgX(s)
Write the equations to test for chloride, bromide, and iodide:

16. Group 8A Elements (ns2np6, n  2)
Completely filled ns and np subshells. Highest ionization energy of all elements.
No tendency to accept extra electrons.
8.6

17. Properties of Oxides Across a Period
(when added to water)
basic
acidic
8.6

18. Reactions of Oxides of Period 3
Oxides of metals react with water to form a base
Na2O (s) H2O (l)  2 Na+ (aq) OH1- (aq)
(NOTE: Mg(OH)2 is not very soluble.)
Write the corresponding equation for magnesium oxide

19. Reactions of Oxides of Period 3
Oxides of metals can act as a base to neutralize an acid to form salt and water.
MgO (s) + 2 HCl (aq)  Mg2+ (aq) + 2 Cl1- (aq) + H2O (l)
Write the corresponding equation for sodium oxide:

20. Reactions of Oxides of Period 3
Oxides of non metals react with water to form acids
CO2 (g) H2O (l)  H+ (aq) HCO31- (aq)
SiO2 (s) + H2O (l)  not much of a reaction, however silicon dioxide will react as an acid to neutralize a base…
SiO2 (s) + 2 OH1- (aq)  SiO3 2- (s) + H2O (l)
P4O10 (s) H2O (l)  4 H+ (aq) H2PO41- (aq)
SO3 (s) H2O (l)  H+ (aq) + HSO41- (aq)

21. neutral acidic Properties of Chlorides Across a Period
(when added to water)
neutral
acidic
NaCl
MgCl2
AlCl3
(Al2Cl6 (g))
SiCl4
PCl3
PCl5
SCl2
Cl2
Type of bonding
ionic
giant covalent
molecular covalent
Structure
crystalline solid
(extensive 3D structure)
solid
liquid
gas
Properties
high melting points
sublimes at 178°C to give vapor
low melting and boiling points
conduct electricity in molten and (aq) states
molten chlorides do NOT conduct electricity
(no ‘charged’ particles)
aqueous chlorides DO conduct electricity
Acid-Base Nature
dissolve when added to water (neutral soln)
react with water to form acidic soln
8.6

22. Reactions of Chlorides of Period 3
NaCl (s) + H2O (l)  Na+ (aq) + Cl- (aq) + H2O (l)
(No reaction, just dissolving)
Write the corresponding equation for magnesium chloride

23. Reactions of Chlorides of Period 3
AlCl3 (s) + 3 H2O (l)  Al(OH)3 (s) + 3 H+ (aq) Cl- (aq)
SiCl4 (l) + 2 H2O (l)  SiO2 (s) + 4 H+ (aq) Cl- (aq)
PCl3 (l) + 3 H2O (l)  P(OH)3 (aq) + 3 H+ (aq) Cl- (aq)
[Note: P(OH)3 (aq) is also known as phosphoric(III) acid H3PO3, a weak acid ]
PCl5 (s) + 4 H2O (l)  H3PO4 (aq) + 5 H+ (aq) Cl- (aq)
[Note: H3PO4 (aq) is known as phosphoric(V) acid, which is a strong acid ]
Cl2 (s) + H2O (l)  H+ (aq) + Cl- (aq) + HOCl (aq)
[Note: HOCl (aq) is known as chloric acid and is a weak acid ]
What patterns do you notice?

24. Ready for Homework? Exercise 3.3 p 80 # 1-10 due: __________
Suggestion –
Work through the problems using the text and notes to answer the questions.
Check your answers with the key.
THEN, try to answer the problems again… without your notes.