Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 109 - General Chemistry - Spring 2011

Lecture Notes 22: 11 March

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Quantum Numbers

This is an alternate way of designating the electrons in an atom. Each electron will have a unique set of quantum numbers.

• Pauli Exclusion Principle: No two electrons in the same atom can have the same value for all quantum numbers. (i.e. no two electrons can occupy the same state).

Note that the Pauli exclusion principle and electron spin mean that a maximum of two electrons may occupy a single orbital.

Atomic Structure & Chemical Periodicity

The Periodic Table

Look at the Periodic Chart. The pattern arises due to a repetition or periodicity of chemical properties. The vertical columns of the charts are called groups, while the rows are referred to as periods.

Note the numbering of the groups. The numbers from 1 - 18 are the internationally accepted numbers. We will also use the I - VIII "American" numbering system. Note that the "tallest" columns comprise what are referred to as the "representative elements" (IA - VIIIA).

Terms:

• Period: the rows of elements showing a repeating pattern of properties (e.g. Na - Ar).
• Group: a vertical column of elements on the table sharing a family resemblance of properties (e.g. Li - Fr).
• Representative elements: the elements of the s-block and p-block (blue and green on the table above).
• Transition metal elements: the elements of the d-block (yellow in the table above).
• Inner-transition metal elements: The f-block or Lanthanides and Actinides (not shown on the table above)
• Groups:
  • IA = alkali metals;
  • IIA = Alkaline earth metals;
  • VIIA = Halogens (note the generic symbol of X standing for any halogen);
  • VIIIA = Noble gases (older = inert gases).

You should know the terminology above.

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© R A Paselk

Last modified 23 March 2011