The Periodic Table — History and Organisation

This lesson covers the history of the periodic table and how it is organised, as required by AQA GCSE Combined Science Trilogy (8464, Chemistry 4.1.2). You need to understand how early attempts to classify elements led to the modern periodic table and why elements are arranged the way they are.

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Early Classification Attempts

Before the periodic table was developed, scientists tried to organise the known elements in various ways:

John Newlands — The Law of Octaves (1866)

• Newlands arranged the known elements in order of atomic mass.
• He noticed that every eighth element had similar properties (like the octave in music).
• His law worked for the first few elements but broke down with heavier elements.
• He did not leave gaps for undiscovered elements.
• Other scientists criticised his work, and it was not widely accepted at the time.

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Mendeleev's Periodic Table (1869)

Dmitri Mendeleev created the first widely accepted periodic table:

Key Features of Mendeleev's Table