1. Chapter 19 The Representative Elements: Group 1A through 4A
Reviewing the Periodic Table Regions:
Representative elements: Groups 1A - 8A - filling s and p orbitals (s and p valence electrons).
Transition elements: Center of the table - filling d orbitals.
Lanthanides, Actinides: listed separately, on the bottom of the table - filling 4f and 5f orbitals.
Metalloids: separate metals from nonmetals, exhibit both metallic and nonmetallic properties.

2. Figure 19.1 The Periodic Table

3. Metals and Nonmetals Metals: Nonmetals:
Lose one or more valence electrons
Form cations (positive ions)
Low ionization energy
Found on the left side of the periodic table
Nonmetals:
Gain one or more electrons
Form anions (negative ions)
Large ionization energy
Most negative electron affinity
Found on the right side of the table

4. Atomic Size and Group Anomalies
Atomic size increases down a group.
Large increase in atomic radius in going from first to second member.
First element shows properties that are quite different from the others.
Hydrogen is a nonmetal but lithium is a very active metal.
BeO is amphoteric but other group 2A oxides are basic.
Usually C forms C-C bonds but Si forms Si-O bonds
N forms :NN: but P forms tetrahedral P4 molecules
O form O2 molecule but S forms bigger aggregates, S8.

5. Figure 19.2 The Atomic Radii of Some Atoms in Picometers

6. Figure 19.3 The Structure of Quartz

7. Metallurgy . . . the process of obtaining a metal from its ore.
This always involves reduction of the ions to the elemental metal (oxidation state = 0).
Reducing agents are used to produce the metals from their ores.
2SnO(s) + C(s) 2Sn(s) + CO2(g)
2PbO(s) + C(s) 2Pb(s) + CO2(g)
SnO(s) + H2(g) Sn(s) + H2O(g)

8. Alkali Metals
The group 1A elements with their ns1 valence electron configurations are very active metals. They lose their valence electrons very readily. They have low ionization energies and react with nonmetals to form ionic solids.
2Na(s) + Cl2(g)  2NaCl(s)
The expected trend in reducing ability, Cs>Rb>K>Na>Li
Alkali metals all react vigorously with water to release hydrogen gas.
2M(s) + 2H2O(l)  2M+(aq) + 2OH-(aq) + H2(g)
Observed reducing abilities: Li>K>Na

9. Group 1A Oxides In the presence of ample oxygen,
4Li + O2  2Li2O (regular oxide)
2Na + O2  Na2O2 (peroxide)
K + O2  KO2 (superoxide)
Rb + O2  RbO2 (superoxide)
Cs + O2  CsO2 (superoxide)

10. Hydrogen
Hydrogen is a color less, odorless gas composed of H2 molecules.
Because of its low molar mass and nonpolarity, hydrogen has a low boiling point (-253oC) and melting point (-260oC).
Industrial source: methane reacts with water at high temp.( oC) and high pressure (10-50 atm) in presence of nickel catalyst
CH4(g) + H2O(g)  CO(g) + 3H2(g)
Hydrogen can be produced by electrolysis of water which is not economically feasible because of the high cost of electricity.
The major industrial use of hydrogen is in the production of ammonia.

11. Hydrides . . . are binary compounds containing hydrogen.
ionic hydrides: hydrogen + the most active metals (e.g, LiH, CaH2)
covalent hydrides: hydrogen + other nonmetals (e.g, H2O, CH4, NH3)
metallic (interstitial) hydrides: transition metal crystals treated with H2 gas.

12. Figure 19.5 The Structure of Ice, Showing the Hydrogen Bonding

13. Alkaline Earth Metals Group 2A elements are very reactive
Valence electron configuration ns2
Lose 2 valence electrons to form noble gas configuration
Form ionic compounds containing M2+ cations
Oxides are basic:
MO(s) + H2O(l)  M2+(aq) + 2OH-(aq)
Ca, Sr, and Ba reacts vigorously with water:
M(s) + 2H2O(l) M2+(aq) + 2OH-(aq) + H2(g)
Be form covalent bond because of small size and high electronegativity

14. The Structure of Solid BeH2

15. Figure 19.6 Preparation for the Group 2A Elements

16. Ion Exchange
Ca2+ and Mg2+ ions cause the hardness of water. These ions of hard water interfere with the action of detergents and form precipitate with soap. Those ions are removed by ion exchange with ion exchange resins.
Ca2+ and Mg2+ are often removed during ion exchange, releasing Na+ into solution.
Ion exchange resin: large molecules that have many ionic sites.

17. Group 3A Elements Valence electron configuration ns2np1.
Increase metallic character in going down the group.
B is a nonmetal and its compounds are covalent.
Boranes are hydride of B: diborane B2H6
Al is the most abundant metal on earth.
Al forms covalent bond with nonmetals
Gallium has unusually low melting point at 29.8oC (Al:660oC)

18. Figure 19.8 The Structure of B2H6

19. Group 4 Elements Valence electron configuration ns2np2
C and Si are the two most important elements on earth
Increase metallic character in going down the group
C is a nonmetal, Si & Ge are semimetals, Sn and Pb are metals
All elements form four covalent bond to nonmetals

20. Group 4 Elements continued…
Form tetrahedral molecules because of sp3 hybridization
Carbon occurs as graphite and diamond
Si forms silica and silicates are the most abundant of the earth crust
Ge used in the manufacture of semiconductors
Sn used in various alloys such as bronze (20% Sn and 8% Cu)

21. Inert Pair Effect
The tendency for the heavier elements of Groups 3A and 4A to exhibit lower oxidation states as well as their expected oxidation states.
Group 3A +1 and +3 oxidation states
Group 4A +2 and +4 oxidation states