After this lesson, you should be able to:

• Understand periodicity by looking into various properties, such as density, melting and boiling points, atomic radii, formulae of halides or oxides, ionization energy, electronegativity and electron affinity
• List similarities in chemical properties among elements in groups 1, 2, 17 and 18, such as reactivity
• Predict chemical properties of elements in groups 1, 2, 17 and 18
• Indicate where metals, nonmetals and transition metals can be found