# Mendeleev arranged the elements in an early version of the periodic table. Describe how Mendeleev arranged the elements in his periodic table and explain why his arrangement was significant.

> Eduqas A-Level Chemistry — 2.1 Periodic table · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Mendeleev arranged the elements in order of increasing atomic weight (atomic mass)
2. Elements with similar chemical properties were placed in the same group (column)
3. Mendeleev left gaps in his table where no known element fitted the pattern
4. The gaps allowed Mendeleev to predict the properties of elements that had not yet been discovered
5. When those elements were later discovered and matched his predictions, his table was accepted / this showed the periodic table was a valid model

## Key terms

- [periodic table](https://www.gradenine.co.uk/glossary/periodic-table)
- [period](https://www.gradenine.co.uk/glossary/period)

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/mendeleev-arranged-the-elements-in-an-e390645a) · Published by Druglandscape Ltd.