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Theoretical Chemistry The Periodic Table Theoretical Chemistry

Origin of Periodic Table Triads - groups of 3 elements with similar properties (Dobereiner – 1817) Law of Octaves – properties of elements repeat every 8 elements (Newlands – 1863)

Origin of Periodic Table Dimitri Mendeleev – 1869 Properties of elements are periodic functions of their atomic masses. Developed 8 column table Left spaces for undiscovered elements Columns contained elements with similar properties Problems with Ni, I, K (Why?)

Origin of Periodic Table X-ray experiments by Mosley (1913) led to discovery of atomic numbers. Modern Periodic Law – properties of elements are periodic functions of their atomic numbers.

Organization of Periodic Table Rows are called periods. Columns are called families or groups. All elements in a family have similar properties. Octet Rule – elements with 8 valence electrons are unreactive

The Periodic Table of Elements The P.T. is made up of Groups/Families (columns) Periods (rows)

The groups are further categorized as follows: 1 8 Main Group (A) 2 3 4 5 6 7 Group B

The groups may also be broken down into (including Hydrogen) Non-Metals Metals (not including Hydrogen)

Each group is then further classified as follows: Alkaline Earth Noble Gases Each group is then further classified as follows: Metalloids Alkali Halogens Transition Metals Stair step Inner Transition Metals

The Inner Transition Metals are classified as follows: Lanthanides Actinides