# Mendeleev arranged the elements into a periodic table. Describe two features of Mendeleev's arrangement of the elements and explain why his ordering was not always correct.

> Eduqas GCSE Chemistry — 2.5 The production of important chemicals · Describe · 4 marks

## Mark scheme (4 marks)

1. Mendeleev arranged elements in order of atomic weights / increasing atomic mass
2. Elements with similar chemical properties were placed in the same group / column
3. Mendeleev left gaps where elements had not yet been discovered / found
4. His ordering was not always correct because different isotopes of an element have different masses / atomic weights

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