2.2 Group 2
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Write an equation for the first ionisation energy of Magnesium
Mg (g) —> Mg+ (g) + e-
What happens to the first ionisation energy of Group 2 as you go down the group? Why?
Decreases because: - Number of filled electron shells increases down the group —> increased shielding, increased atomic radius —> weaker force between outer electron and nucleus —> less energy needed to remove electron
Why does the graph of first ionisation energies across period 2 look like that?
First ionisation energy increases because of increased nuclear charge, decreased atomic radius, and same electron shielding means more energy is needed to remove the first electron - Dips at Al, outer electron is in 3p orbital, higher energy than 3s orbital —> less energy needed to remove first electron - Dips at S because one 3p orbital has 2 spin paired electrons, repulsion between paired electrons —> less energy needed to remove one
How does reactivity with water change as you go down group 2?
Increases Mg least —> Ba most Because outer electrons further from nucleus and more electron shielding, so electrons are lost more easily
Write an equation for the reaction of Barium and water
Ba (s) + 2H2O (l) —> Ba(OH)2 (aq) + H2 (g)
Write an equation for the reaction of magnesium and steam
Mg (s) + H2O (g) —> MgO (s) + H2 (g)
What is the trend in hydroxide solubility as you go down the Group?
Increases down the group Mg(OH)2 is nearly insoluble Ba(OH)2 creates a strong alkaline solution
What is the trend in sulphate solubility down group 2?
Decreases down the group MgSO4 is soluble BaSO4 is insoluble
What is the trend in melting point down group 2 ? Why?
Decreases down group Because sea of delocalised electrons is further from positive charge of the nucleus —> weaker metallic bonds / forces of attraction which take less energy to weaken
What is the trend in atomic radius going down group 2?
Increases as there are more occupied electron shells down the group
Write the equations for the extraction of Titanium using Magnesium
TiO2 + 2Cl2 + C —> TiCl4 + CO2 TiCl4 (l) + 2Mg (s) —> 2MgCl2 (s) + Ti (s)
What are flue gases
Gases produced by power stations which are harmful to the environment
How can CaO or CaCO3 be used to remove flue gases? Write the equations
CaCO3 (s) + SO2 (g) —> CaSO3 (s) + CO2 (g) CaO (s) + SO2 (g) —> CaSO3 (s)
What is Ca(OH)2 used for? Write an equation related to one of its uses
Used to neutralise soil Ca(OH)2 (aq) + 2HCl (aq) —> 2H2O (l) + CaCl2 (aq)
What is Mg(OH)2 used for ?
Milk of magnesia - antacid to treat heartburn, wind, indigestion
What is a use of BaSO4 ? Why is it safe?
In barium meals to outline gut in X-Rays Ba2+ is toxic but barium sulphate is insoluble
How can BaCl2 be used to test for sulphate ions?
Add to sample with HCl, white ppt will form if sulphate ions present Ba2+ + SO4(2-) —> BaSO4