The Periodic Table

This lesson covers the structure and history of the periodic table, as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand how the periodic table is organised, why elements in the same group share similar properties, and the contribution of Mendeleev to its development.

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Structure of the Modern Periodic Table

The modern periodic table arranges all known elements in order of increasing atomic (proton) number. It is organised into:

Groups (Columns)

• There are 8 main groups (plus transition metals in the middle).
• Elements in the same group have the same number of electrons in their outer shell.
• This gives them similar chemical properties.

Periods (Rows)

• There are 7 periods.
• Elements in the same period have the same number of electron shells.
• Moving across a period from left to right, the atomic number increases by one each time.

Metals and Non-Metals