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The Representative Elements: Groups 1A Through 4A | CHEM 162, Study notes of Chemistry

University of Washington (UW) - SeattleChemistry

Prof. Jene. Material Type: Notes; Class: GENERAL CHEMISTRY; Subject: Chemistry; University: University of Washington - Seattle; Term: Winter 2007;

Typology: Study notes

Pre 2010

Uploaded on 03/18/2009

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Chapter 18. The Representative Elements:
Groups 1A Through 4A
18.1 A Survey of the Representative
Elements
18.2 The Group 1A Elements
18.3 The Chemistry of Hydrogen
18.4 The Group 2A Elements
18.5 The Group 3A Elements
18.6 The Group 4A Elements
The ignition of hydrogen soap bubbles.
Figure 18.1: The periodic table.
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Download The Representative Elements: Groups 1A Through 4A | CHEM 162 and more Study notes Chemistry in PDF only on Docsity!

Chapter 18. The Representative Elements:

Groups 1A Through 4A

18.1 A Survey of the Representative Elements

18.2 The Group 1A Elements

18.3 The Chemistry of Hydrogen

18.4 The Group 2A Elements

18.5 The Group 3A Elements

18.6 The Group 4A Elements

The ignition of hydrogen soap bubbles.

Figure 18.1: The periodic table.

Figure 12.39: Special names for groups

in the periodic table

Figure 12.39: Special names for groups

in the periodic table (contโ€™d)

Crystalline beryl from Colombia: Source of Be

Source: Photo Researchers, Inc.

Figure 18.6: The Structure of BeH 2 Solid;

A polymeric network structure

โ†’ three-center bond in Be-H-Be

  • one electron pair is shared among 3 atoms

Be

H

Be

H

H

Be

H

H

H

Figure 18.7: Solid BeCl 2 can be visualized as

consisting of many BeCl 2 molecules

Solid

  • linear molecule
  • sp hybridized Be
  • Be-Cl bonds are covalent

Solid BeCl 2

  • a tetrahedral network

Table 18.8 Selected Reactions of the Group 2A Elements

Rxns forming halides, oxides, nitrides, hydrides. etc. โ†’ Some practical significance of alkaline earth metals

  • Ca2+^ and Mg 2+^ are essential for human life

bones and teeth

metabolism and muscle functions

โ€” many other biochemical functions in the body

  • Ca2+^ and Mg 2+^ ions in water supplies result in the water being hard i.e. they form precipitates with soap, interfering with the action of soap / detergents โ€” Removal by ion exchange

Table 18.10 Selected Reactions of the Group 3A Elements

โ†’ Boron

  • covalent compounds typical of nonmetals
  • boranes (covalent hydrides of boron)
  • diborane (B 2 H 6 ) is the simplest stable borane

Note the three-center B-H-B bridging bonds in boranes

Fig. 18.9: The structure of boranes.

Halides: BCl 3 , AlCl 3 , GaCl 3 , InCl 3 , etc. โ€” strong Lewis acids Oxides: e.g. Al 2 O 3 โ† amphoteric, dissolves in acidic or basic solution

โ†’ Aluminum

  • most abundant metal on earth
  • metallic physical properties โ€” high electrical and thermal conductivities
  • Melting point = 660โ„ƒ โ†’ Gallium
  • melting point = 29.8 โ„ƒ โ† very unusual for a metal
  • boiling point = 2400 โ„ƒ โ† a liquid over a large range

Gallium melts in the hand

โ†’ Indium, Thallium Both +3 and +1 oxidation states are common Inert pair effect, the tendency of heavier members of a group to exhibit the +1 and +3 oxidation states (need relativistic quantum mechanical model of the atom).

โ†’ Importance of group 3A elements

  • Aluminum is widely used as a structural material in many applications (highly strength - to- weight ratio) โ€” aircraft bodies โ€” bicycle components
  • Gallium in the form of GaAs โ† compound semiconductor โ€” high speed electronic chips and systems (faster than Si-based computers) For military, space, and other specialized applications.

18.6 Group 4A Elements

4A

C

Si Ge Sn Pb

nonmetal Semimetals (semiconductors)

metals

ns 2 np 2 valence electron configuration

Sand is composed of silicon and oxygen.

Lead (II) oxide, PbO (also called litharge)

Tin

Lead

  • +2 and +4 oxidation states, e.g. PbO, PbCl 4 , and Pb 3 O (^4)
  • lead poisoning: from drinking water pipes, lead-based paints, tetraethyl lead in gasoline, lead storage batteries in automobiles, etc.
  • Apparently Beethoven died (at 56) from lead poisoning.

Figure 18.1: The periodic table.