Group 2 Metals Flashcards
How does atomic radium change down the group?
Increases
Extra electron shell, outer electron further from nucleus and more shielded
Increased nuclear charge outweighed by greater shielding and distance
How does first ionisation energy change down the group?
Decreases down the group
Extra electron shell, outer electron further from nucleus and more shielded
Increased nuclear charge outweighed by greater shielding and distance
How does electronegativity change down the group?
Less electronegative down the group
As bonding pair is further away from the nucleus
How do melting and boiling points change down the group?
Decrease
Metallic bonding gets weaker down the group
Ionic radius of metal ions increases down group so charge density decreases. Weaker attraction between metal ions and delocalised electrons
How does atomisation energy change down the group?
It decreases due to weaker metallic bonding
Increased shielding and greater atomic radius
What is the equation for the reaction Mg and water?
Mg(s) + H20(g) to MgO(s)+ H2(g)
What is the equation for the reaction Ca and water?
Ca(s) + 2H2O(l) to Ca(OH)2(s) + H2(g)
What is the equation for the reaction Sr and water?
Sr(s) + 2H2O(l) to Sr(OH)2(aq) + H2(g)
What is the equation for the reaction Ba and water?
Ba(s) + 2H2O(l) to Ba(OH)2(aq) + H2(g)
How does reactivity with water change down the group?
Since ionisation energies decrease down a group, the electrons are more easily removed from the atoms and the reaction with water becomes increasingly vigorous on descending group II.
what is the trend in solubility of the sulphates?
The solubility of the sulphates decreases down group II
MgSO4 is soluble, CaSO4 is sparingly soluble and SrSO4 and BaSO4 are insoluble
Barium is insoluble, how can this be used?
To test for the presence of sulphate ions, SO4
What is the trend in solubility of the hydroxides?
As solubility increases, more OH- ions are released.
This makes a more alkaline solution.
The pH increases down the Group
How can adding hydroxides to group 2 metals identify them?
As Mg(OH)2 is sparingly soluble, a thick white precipitate is formed. As Ba(OH)2 is more soluble, a thin white precipitate will be formed
How can adding sulphates to group 2 metals identify them?
As MgSO4 is soluble, no precipitate will form.
As BaSO4 is insoluble, a white precipitate will be formed.
What is the test for sulphate ions?
Add HCl first – This reacts and removes any sulphites or carbonates that may also give a white precipitate.
Add BaCl2 solution: If sulphates are present, a white precipitate of BaSO4 will form.
What is the equation for the reaction between barium and sulphate ions?
Ba2+(aq) + SO42-(aq) to BaSO4(s)
In the flame test what colour will calcium strontium and barium burn?
Ca+ - brick red
Sr2+ - red
Ba2+ - pale green
How can barium have a medical application?
Barium sulphate, BaSO4, does not allow X – rays to pass through.
Drinking a suspension of BaSO4 coats the oesophagus, stomach or intestines (Barium
meal)
These now show up on an X – Ray allowing you to see any problems.
Other Group 2 metal compounds are soluble so cannot be used.
How can group 2 metals help in the extraction of titanium? Give an equation:
TiO2 is converted to TiCl4 by heating with carbon and chlorine
TiCl4 is then reduced by Mg:
TiCl4(g) + 2Mg(l) to Ti(s) + 2MgCl2(l)
Magnesium reduces titanium
How can you remove SO2 from flue gases?
SO2 is produced burning fossil fuels to make electricity.
This can be removed by reacting with an alkali such as CaO or CaCO3 slurry (mixed with
water)
Give the equations for the extraction of SO4 from flue gases:
CaO(s) + 2H2O(l) + SO2(g) à CaSO3(aq) + 2H2O(l)
CaCO3(s) + 2H2O(l) + SO2(g) à CaSO3(aq) + 2H2O(l) + CO2(g)
How can the alkaline earth metals neutralise acids?
Ca(OH)2 is used to neutralise acidic soils.
Mg(OH)2 is used to neutralise excess stomach acids as milk of magnese
