Periodicity revision notes

Periodicity revision notes for OCR A F321


Periodicity revision notes

Periodicity – the trends that occur (in physical and chemical properties) as you move across the periods.

As you move across the periodic table metals change to non-metals and solids change to gasses.

Atomic radius

·         Atomic radius decreases across a period, as the number of protons increase the charge of the nucleus becomes more positive, so electrons as pulled in slightly closer.

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Ionisation energy trends

Ionisation energy

·         Ionisation energy increases across a period due to:

1.    Atomic radius – the further the outer shell electrons from the nucleus, the lower the ionisation energy.

2.    Nuclear charge – the more protons in the nucleus, the higher the ionisation energy.

3.    Electron shielding – the more inner shells there are, the more shielding there is, and the lower the ionisation energy.

·         Ionisation energy decreases down a group due to:

1.    Elements further down the group have more electron shells, so there is more shielding, so electrons can be removed more easily.

2.    Less attraction from the nucleus.

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Melting and boiling point trends

Melting and boiling points

·         For metals, melting and boiling points increase across the period as the metallic bonding gets stronger. This is due to metal ions having an increasing number of delocalised electrons and a decreasing ionic radius, so there is a decreasing ionic radius.

·         From group 1 to 3 there is an increase in boiling points, as there is metallic bonding – strong forces between positive metal ions and delocalised electrons

·         From group 4 there is a sharp decrease in boiling point, as there is giant covalent bonding, which are strong forces between atoms, weaker than metallic bonds.

·         From group 5 to 0 there are comparatively low boiling points, as there are van der Waals’ forces, which are weak forces between molecules.

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