Module 3

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Periodic table

Then- Mendeleev arranged 60 elements in order of atomic mass. Put into groups with similar properties. Swapped around elements and left gaps, assuming there were elements that had not yet been discovered, predicting some of their properties.

Now- 114 elements. Arranged in 7 periods and 18 groups.

Arranged in;

-Atomic number

-Groups- atoms with the same number of outer shell electrons and similar properties.

-Periods and periodicity- Period gives you the highest energy electron shell in in an element's electron. Periodicity is repeating trends in properties in elements. Looks at; electron configuration, ionisation energy, structure and melting points.

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