CHEMISTRY         S.S.S.2   First term

WEEK 2

Periodic table 2

Performance objectives

Students should be able to:

1. Explain the diagonal relationship between at least two elements in the periodic table.
2. Define ionization energy and state its trend across the period and down the group
3. Define electron affinity and state its trend across the period and down the group

Content

Periodicity of fundamental properties

Periodicity is the variation of properties of elements across the period and down the group. The key to the periodicity of elements lies in the electronic configuration of atoms. It is to be expected, therefore, that any physical properties connected with electron arrangement will also experience this periodicity. Such physical properties include ionization energy, melting and boiling point, electron affinity, atomic radii, ionic radii, electronegativity, electrical and thermal conductivities, etc.

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