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Period (Chemistry)

Key Stage 3

Meaning

A period is a row on the Periodic Table whose elements all have the same number of Electron Shells.

About Periods

Atomic Number increases as you move along a period.
PeriodicTablePeriods.png

Trends within Periods

The chemical and physical properties of elements change as you move along a period.
Period 2 Melting Points Period 3 Melting Points
Period2MeltingPoints.png
Period3MeltingPoints.png
There is a trend in the Melting Points as you move along the period. A similar trend can be seen in the next period.

Key Stage 4

Meaning

A period is a row on the Periodic Table whose elements all have the same number of Electron Shells.

About Periods

Atomic Number increases as you move along a period.
The number of the period is the same as the number of electron shells.

Trends within Periods

Period2ElectronShells.png
Period2ElectronShielding.png
For the first 3 elements Lithium, Beryllium and Boron all lose electrons in chemical reactions.

The reactivity decreases as you go across the period because:

Nitrogen, Oxygen and Fluorine can all gain electrons to become negative ions in certain reactions.

The reactivity increases as you go across the period because: