Group 2, the alkaline earth metals

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  • Created by: r98
  • Created on: 07-04-16 17:15
Why are the elements in Group 2 referred to as the alkaline earth metals?
Because their oxides and hydroxides are alkaline.
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Does the atomic (metallic) radii increase or decrease as you go down the group?
Increase, because each element has an extra filled main level of electrons compared with the one above it.
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Does the melting point increase or decrease as you go down the group, starting with calcium?
Decrease, because the sea of delocalised electrons gets further away from the positive nuclei, resulting in a decrease in the strength of the metallic bonds.
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How does magnesium's melting point compare to the other Group 2 elements? Why does magnesium not fit the trend in melting points?
Magnesium has the lowest melting point, because the lattice arrangement of atoms is different from that of the elements below, which makes them slightly easier to separate.
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What happens to atoms of elements in Group 2 in all reactions?
They lose their two outer electrons, to form ions with two positive charges.
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What is the trend in ionisation energy as you go down the group?
Both the first and second ionisation energy decrease going down the group, because it takes less energy to remove electrons as they become further away from the positive nucleus. The nucleus is more shielded.
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In all their reactions, do the metals get more or less reactive as you go down the group?
The metals get more reactive, going down the group.
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In all their reactions are the Group 2 metals (Mg to Ba) oxidised or reduced? What's the change in their oxidation state? What type of reaction are these?
They're oxidised, as they lose electrons. The metals go from an oxidation state of 0 to +2. These are redox reactions.
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When the Group 2 elements react with water, what's the trend in reactivity going down the group?
The metals get more reactive as you go down thr group.
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Using 'M' to represent any Group 2 metal, what's the equation for the basic reaction with water?
M(s) + 2H2O(l) -----> M(OH)2(aq) + H2(g)
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What is another name for magnesium hydroxide? What is a use of Mg(OH)2?
Milk of magnesia. It's used in indigestion remedies to neutralise excess stomach acid.
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With reference to speed of reactions, how does magnesium reacting with water compare to it reacting with steam?
Magnesium reacts very slowly with water, but rapidly with steam.
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What is the equation for the reaction between magnesium and steam?
Mg(s) + H2O(g) -----> MgO(s) + H2(g)
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What is another name for calcium hydroxide? How can it be used?
Slaked lime. It's used to treat acidic soil
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What is the colour and state of all the hydroxides?
They're all white solids.
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What is the trend in the solubility of the hydroxides, going down the group?
The solubility of the hydroxides increases, as you go down the group.
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What can be said about the solubility of Mg(OH)2? Is it sold in solution?
It's almost insoluble. It's sold as a suspension in water rather than a solution.
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What can be said about the solubility of Ca(OH)2? What is it used as, in solution?
It's sparingly soluble. A solution is used as lime water.
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How does the solubility of strontium hydroxide, Sr(OH)2, compare to that of calcium hydroxide, Ca(OH)2?
Sr(OH)2 is more soluble.
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What is produced when barium hydroxide dissolves?
A strongly alkaline solution.
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What's the equation of barium hydroxide dissolving?
Ba(OH)2(s) + aq -----> Ba^(2+)(aq) + 2OH-(aq)
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What's the trend in the solubility of the sulfates as you go down the group?
The sulfates become less soluble, as you go down the group.
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How can the solubility of barium sulfate be described?
It's virtually insoluble.
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What is another name for barium sulfate? What is a use of it?
Barium meal. Taken by mouth, to outline the gut in medical x-rays (the heavy barium atom is good at absorbing x-rays).
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Why is barium sulfate used in medicine, eventhough it's highly toxic?
Because barium sulfate is so insoluble.
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What is another use of barium sulfate?
Used in a simple test for sulfate ions in solution.
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What are the steps involved when testing for sulfate ions? What would the observations be of a positive result?
First, the solution is acidified using nitric acid or hydrochloric acid. Then barium chloride solution is added to the solution. If sulfate ions are present, a white ppte of barium sulfate is formed.
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What is the equation for the formation of barium sulfate?
Ba^(2+)(aq) + SO4^(2-)(aq) -----> BaSO4(s)
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Why is acid added first when testing for sulfate ions?
The addition of acid removes carbonate ions as carbon dioxide. (Barium carbonate is also a white solid, so would be indistinguishable from barium sulfate).
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What is a use of magnesium sulfate?
The hydrated salt (Epsom salts) is used as a mild laxative. It's soluble in water and is found in bath salts.
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Other cards in this set

Card 2

Front

Does the atomic (metallic) radii increase or decrease as you go down the group?

Back

Increase, because each element has an extra filled main level of electrons compared with the one above it.

Card 3

Front

Does the melting point increase or decrease as you go down the group, starting with calcium?

Back

Preview of the front of card 3

Card 4

Front

How does magnesium's melting point compare to the other Group 2 elements? Why does magnesium not fit the trend in melting points?

Back

Preview of the front of card 4

Card 5

Front

What happens to atoms of elements in Group 2 in all reactions?

Back

Preview of the front of card 5
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