1. Midterm is Friday, March 24 Chapters 5-8 (except today’s material)
Important reminder!
Midterm is Friday, March 24
Chapters 5-8 (except today’s material)
4/6/2019

2. Group 1A elements (ns1, n  2)
M M+1 + 1e-
2M(s) + 2H2O(l) MOH(aq) + H2(g)
metal hydroxides
4M(s) + O2(g) M2O(s)
metal oxides
Increasing reactivity
4/6/2019

3. Alkali Metals
Alkali metals (except Li) react with oxygen to form peroxides (O22- anion):
2Na + O2  Na2O2
K, Rb, and Cs also form superoxides (O2- anion):
K + O2  KO2
Alkali metal ions colorless, but produce bright colors when placed in flame.
4/6/2019

4. Group 2A elements (ns2, n  2)
M M+2 + 2e-
Be(s) + 2H2O(l) No Reaction
Mg(s) + 2H2O(g) Mg(OH)2(aq) + H2(g)
M(s) + 2H2O(l) M(OH)2(aq) + H2(g) M = Ca, Sr, or Ba
BeO and MgO form at elevated temperatures; CaO, StO, and BaO form at rt.
Increasing reactivity
4/6/2019

5. Mg(s) + 2H2O(l) Mg(OH)2(aq) + H2(g)
Alkaline earth metals
Be does not react with water, Mg reacts only with steam, but others react readily with water.
Reactivity tends to increase as go down group.
Mg(s) + 2H2O(l) Mg(OH)2(aq) + H2(g)
4/6/2019

6. Group 3A elements (ns2np1, n  2)
B is a metalloid; boron does not form binary ionic compounds and is unreactive
toward O2 and H2O.
Al is most abundant metal in Earth’s
crust, found as aluminosilicates.
rest of Group 3A are metals
4Al(s) + 3O2(g) Al2O3(s)
Bauxite is chief ore of Al.
2Al(s) + 6HCl(aq) AlCl3(s) + 3H2(g)
4/6/2019

7. Group 3A elements (ns2np1, n  2)
Aluminum forms only tripositive ions.
Other 3A elements form both +3 and +1 states with +1 becoming more stable
going down the group
4/6/2019

8. Thermite reaction 2Al(s) + Fe2O3 Al2O3(l) + 2Fe(l) ΔH= -847.6 kJ/mol
Enough heat released to raise the temperature to ~3000 oC which causes
the products to be molten.
This reaction is often used to weld iron and steel (alloys of Fe) parts together.
4/6/2019

9. Booster rockets
10Al(s) + 6NH4ClO Al2O3(l) + 2AlCl3(l) + 12H2O(g) + 3N2(g)
Enough heat released to raise the temperature to 3200 oC which causes
2 gases to expand rapidly.
The expanding water vapor and nitrogen lift the rocket boosters with a tremendous force. All the fuel is burned in about two minutes.
4/6/2019

10. Group 3A elements (ns2np1, n  2)
Aluminum forms only tripositive ions.
Other 3A elements form both +3 and +1 states with +1 becoming more stable
going down the group
Metallic elements also form many molecular compounds.
AlH3 resembles BeH2 (diagonal relationship, gradual shift from metallic
to nonmetallic character from left to right across the periodic table.
4/6/2019

11. Group 4A elements (ns2np2, n  2)
C nonmetal, Si & Ge metalloids, Sn & Pb metals
Sn(s) + 2H+(aq) Sn2+(aq) + H2 (g)
Pb(s) + 2H+(aq) Pb2+(aq) + H2 (g)
4/6/2019

12. Group 4A elements (ns2np2, n  2)
4A elements form compounds in +2 and +4 oxidation states.
For C and Si, +4 oxidation state is more stable.
CO2 more stable than CO
SiO2 exists; SiO does not (under normal conditions)
+4 is only slightly more stable for Sn; +2 is more stable for Pb
4/6/2019

13. Group 5A elements (ns2np3, n  2)
N & P nonmetals, As & Sb are metalloids, Bi is a metal
Elemental N exists as N2
NO, N2O, NO2, N2O4, and N2O5
N accepts 3 e- to form nitride, N3- (most metallic nitrides
are ionic compounds)
4/6/2019

14. Group 5A elements (ns2np3, n  2)
P exists as P4 molecules, forms P4O6 and P4O10
2 important oxoacids:
N2O5(s) + H2O(l) HNO3(aq)
P4O10(s) + 6H2O(l) H3PO4(aq)
4/6/2019

15. Group 6A elements (ns2np4, n  2)
O, S, Se nonmetals; Te, Po metalloids
O exists as O2
S and Se are S8 and Se8
O, S, Se, Te form dianions by accepting 2 e-
O forms a large number of molecular compounds with
nonmetals
4/6/2019

16. Oxygen Two allotropes: Three anions:
O3, ozone
Three anions:
O2−, oxide
O22−, peroxide
O21−, superoxide
Tends to take electrons from other elements (oxidation)
4/6/2019

17. Group 6A elements (ns2np4, n  2)
Important compounds of S are SO2, SO3, and H2S.
Formation of sulfuric acid:
SO3(g) + H2O(l) H2SO4(aq)
4/6/2019

18. Group 7A elements (ns2np5, n  2)
All halogens are nonmetals and exist as X2
2F2(g) + 2H2O(l) HF(aq) + O2(g)
Increasing reactivity
4/6/2019

19. Halogens Large, negative electron affinities
Therefore, tend to oxidize other elements easily
React directly with metals to form metal halides
Chlorine added to water supplies to serve as disinfectant (HOCl)
4/6/2019

20. Group 7A elements (ns2np5, n  2)
Halogens have high IE and large negative EA
X + 1e X-1
(halides)
X2(g) + H2(g) HX(g)
Form ionic compounds with alkali and alkali earth metals
Form molecular compounds among themselves (ICl, BrF3)
and with nonmetals (NF3, PCl5, and SF6)
Increasing reactivity
4/6/2019

21. Group 7A elements (ns2np5, n  2)
X2(g) + H2(g) HX(g)
(when X=F, explosive)
Hydrogen halides dissolve in H2O to form hydrohalic acids
HF is a weak acid (weak electrolyte)
HCl, HBr, HI strong acids (strong electrolytes)
Increasing reactivity
4/6/2019

22. Group 8A elements (ns2np6, n  2)
Completely filled ns and np subshells. Highest ionization energy of all elements.
No tendency to accept extra electrons.
4/6/2019

23. Noble, but not completely inert
Xe forms three compounds:
XeF2
XeF4 (at right)
XeF6
Kr forms only one stable compound:
KrF2
The unstable HArF was synthesized in 2000.
4/6/2019

24. Properties of oxides across a period
basic
acidic
4/6/2019

25. Properties of oxides across a period
basic
acidic
Classified as acidic or basic depending on whether they produce acids or bases when dissolved in water.
Na2O(s) + H2O(l) -> 2NaOH(l)
Classified as acidic or basic depending on whether they react with acids or bases in certain processes.
Al2O3(s) + 6HCl(aq) -> 2AlCl3(aq) + 3H2O(l)
Al2O3(s) + 2NaOH(aq) + 3H2O -> 2NaAl(OH)4(aq)
4/6/2019

26. Properties of oxides across a period
basic
acidic
Classified as acidic or basic depending on whether they produce acids or bases when dissolved in water.
Classified as acidic or basic depending on whether they react with acids or bases in certain processes.
CO & NO are neutral; they do not react with H2O to produce an acidic
or basic solution.
As the metallic character of the elements decreases from left to right across the period, their oxides change from basic to amphoteric to acidic.
4/6/2019