Periodic Properties of Elements

Periodic Trends in the Periodic Table

Learning Objectives

• Describe and rationalize the periodic properties of elements.

Why Periodic Trends?

• When atoms interact to form chemical species, several factors are crucial:

  • How tightly their valence electrons ($e^{-}$) are held: This depends on the effective nuclear charge ($Z_{eff}$) and the distance of the electrons from the nucleus (principal quantum number, $n$).

  • Ease of losing an electron: Measured by Ionization Energy (I.E.).

  • Desire for gaining or sharing an electron: Measured by Electron Affinity (E.A.).

Shielding & Effective Nuclear Charge ($Z_{eff}$)

• Fundamental Principle: Many properties of an atom are determined by how strongly its valence electrons are attracted by the nucleus and the magnitude of the positive charge they experience.

• Shielding: Electrons located between the electron of interest and the nucleus (core electrons) partially cancel out some of the positive nuclear charge, thus