Chemistry 217

Unit 7
Periodic Properties of the Elements

Unit 6 introduced the quantum mechanical model of electronic structure in atoms. Unit 7 shows how this model can be used to explain variations in atomic properties throughout the periodic table. Atomic radius, ionization energy, and electron affinity are atomic properties with periodic trends that can be explained by configurations and the concepts of shielding and effective nuclear charge. These atomic properties have an effect on the chemical behaviour of different elements. For example, in Unit 8, we consider the importance of ionization energy and electron affinity in explaining the strength of lattice energies in ionic solids.

Objectives

After completing this unit, you should be able to

1. describe the effects of increasing nuclear charge and increasing numbers of electrons on the radial distribution of electron density in many-electron atoms.
2. explain the trends in atomic and ionic radii of elements, and predict the relative size of atoms and ions based on their positions in the periodic table.
3. explain the observed successive ionization energies for an element in terms of its ground state electron configuration.
4. explain the trends in the first ionization energies of elements in terms of ground state electron configurations, and relate these trends to trends in atomic radii.
5. explain the trends in the electron affinities of elements.
6. distinguish between metallic and nonmetallic elements in terms of their characteristic properties and their position in the periodic table.
7. write a balanced chemical equation for the reaction of a given metal oxide with water or a given acid.
8. write a balanced chemical equation for the reaction of a given nonmetal oxide with water or a given base.
9. state the trends in the metallic or nonmetallic behaviour of the elements.
10. write balanced equations for the reaction of active metals with oxygen, hydrogen, sulphur, the halogens, and water.
11. compare Group 1A and Group 2A metals with respect to electron configuration, ionization energy, atomic radius, relative chemical reactivity, charge on ions formed, hardness, density, and melting point.
12. compare elements within each of Groups VIA, VIIA, and VIIIA with respect to electron configuration, ionization energy, atomic radius, density, and melting point.