Group 2, the alkaline earth metals
- Created by: ED
- Created on: 22-03-15 21:19
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- Group 2
- Physical properties
- Oxides and hydroxides are alkaline.
- S-block elements
- Down the group
- Larger atomic radius
- More electron shells
- Outer electrons are further away from positive nucleus
- Strength of metallic bond decreases hence lower melting & boiling points.
- Magnesium does not fit the trend because its lattice arrangement is different hence is easier to separate
- First and second ionisation energies decrease due to more effective electron shielding
- Metals
- Chemical properties
- Reacting with (cold) water forms hydroxides and hydrogen and is slow
- Down the group reactions with water are more reactive
- X(s)+2H2O(l) ->X(OH)2(aq) + H2(g)
- Magnesium hydroxide is "milk of magnesia"
- Used in indigestion remedies to neutralise excess stomach acid
- Reacting with steam is rapid and forms an alkaline oxide and hydrogen
- X(s)+H2O-> XO(s)+H2(g)
- Calcium hydroxide, slaked lime, is used to treat acidic soil.
- They all create white precipitates but down the group the hydroxides become more soluble
- Magnesium hydroxide is (almost) insoluble
- Calcium hydroxide is sparingly soluble
- Strontium hydroxide is (more/ extremely) soluble
- Barium hydroxide is soluble and dissolves to make a strongly alkaline solution
- Sulfates
- Unlike hydroxides, sulfates are less soluble down the group
- Barium Sulfate, BaSO4, is (virtually) insoluble hence used in medicine to outline the gut in medical X-rays
- It is taken by the mouth as "Barium meal" and the heavy barium atom is good at absorbing X-rays.
- Barium compounds are highly toxic but barium sulfate is insoluble hence safe.
- Reacting with (cold) water forms hydroxides and hydrogen and is slow
- X->(X^2+)+e-
- Physical properties
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