The Periodic Table - Periods and Groups

• The ionisation energy shows a general increase across each period

• There is abig decrease after each noble gasbecause: new shell; more shielding; greater distance from nucleus to outer shell

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 Generally across a period:

• Number of protons increases, so more attraction acting on electrons

• Electrons are being added to the same shell - the outer shell is drawn in slightly, decreasing the atomic radius

• Electron shielding will not change

• Nuclear charge increases

• Greater attraction

• The first ionisation energy shows a general decrease down a group

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Generally down a group:

• Number of shells increases, so the distance from the nucleus to outer electrons increases (so a weaker force of nuclear attraction)

• More inner shells - increased shielding

• The atomic radius increases because there is less attraction so the electrons are not pulled as close to the nucleus

• Solubility and alkalinity increases down the group

• Reactivity increases down the group - this reflects the increased ease of losing the outer electrons (vigorous reaction with water increases down the group due to the trends shown down a group)

• Ease of thermal decomposition decreases as you go down the group

• Boiling point increases down the group because as you move down the number of electrons increases, leading to an increase in van der Waals forces between molecules

• Reactivity decreases down the group - due to the trends shown down a group