3.2.2 Group 2, the alkaline earth metals

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  • Created by: KateStoc
  • Created on: 21-05-18 17:57
Explain the trends in atomic radius and first ionisation energy for Alkaline Earth Metals
As you go down the group, atomic radius increase and first ionisation energy decreases because the outer electron is further away from the nucleus.
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Explain the melting point of the elements in terms of their structure and bonding for the Alkaline Earth Metals.
Melting point generally decreases down the group because they all have a typical metal structure.There are no more electron, but larger atomic radius meaning there is less energy needed to break bonds.
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Explain why magnesium does not fit into the general trend for melting points.
Magnesium has a different crystal structure (it has a lower melting point than the trend suggests)
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The reactions of the elements Mg–Ba with water (Written)
All Earth metals are oxidised from 0 to +2 (+2 ion). They form a metal hydroxide and hydrogen gas. Reactivity increases down the group due to decreasing 1st ionisation energy.
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The reactions of the elements Mg–Ba with water (Symbols)
M -> M2+ + 2e- . M(s) + 2H2O(l) -> M(OH)2(aq) + H2(g)
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The use of magnesium in the extraction of titanium from TiCl4 (words)
TiO2 is heated with carbon and a stream of chlorine gas. The TiCl4 is purified by fractional distillation, before being reduced by magnesium in a furnace at ~1000 oC.
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The use of magnesium in the extraction of titanium from TiCl4 (Symbols)
TiCl4(g) + 2Mg (l) -> Ti(s) + 2MgCl2(l)
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The relative solubilities of the hydroxides of the elements Mg–Ba in water.
Solubility of (OH-) increased down the group. Mg is least soluble (insoluble) and Ba is the most soluble.
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The relative solubilities of the sulfates of the elements Mg–Ba in water.
Solubility of (SO4 2-) decreased down the group. Mg is most soluble and Ba is the least soluble.
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The use of Mg(OH)2 in medicine.
Used in indigestion tablets as an antacid. It is safe because Mg(OH)2 is sparingly soluble.
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The use of Ca(OH)2 in agriculture.
Used to neutralise acidic soils (also called slaked lime)
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The use of CaO or CaCO3 to remove SO2 from flue gases (Written).
Acidic SO2 can be removed by reacting with an alkali. A slurry is made by mixing CaO/CaCO3 with water then spraying into flue gases. They react and produce solid calcium sulfite.
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The use of CaO or CaCO3 to remove SO2 from flue gases (Symbols).
CaO(s) + 2H2O(l) + SO2 -> CaSO3(s) + 2H2O(l). CaCO3(s) + 2H20(l) -> CaSO3(s) + 2H20(l) + CO2(g)
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The use of acidified BaCl2 solution to test for sulfate ions.
Add HCl then barium Sulfide to solution. If sulfate ions are present a white precipitate will form (BaSO4). You need to acidify it to remove carbonate or sulfite ions which would give a false positive.
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The use of BaSO4 in medicine.
BaSO4 is called a Barium Meal which is a suspension of BaSO4 (NOT a solution). It is used when someone needs an X-ray of their digestive system because BaSO4 will show up on X-rays. The BaSO4 is insoluble so posed no risk to the patient.
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Other cards in this set

Card 2

Front

Melting point generally decreases down the group because they all have a typical metal structure.There are no more electron, but larger atomic radius meaning there is less energy needed to break bonds.

Back

Explain the melting point of the elements in terms of their structure and bonding for the Alkaline Earth Metals.

Card 3

Front

Magnesium has a different crystal structure (it has a lower melting point than the trend suggests)

Back

Preview of the back of card 3

Card 4

Front

All Earth metals are oxidised from 0 to +2 (+2 ion). They form a metal hydroxide and hydrogen gas. Reactivity increases down the group due to decreasing 1st ionisation energy.

Back

Preview of the back of card 4

Card 5

Front

M -> M2+ + 2e- . M(s) + 2H2O(l) -> M(OH)2(aq) + H2(g)

Back

Preview of the back of card 5
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