Group 2
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Does atomic radius increase or decrease down the group?
Atomic radius gets larger down the group due to extra shielding from electrons.
Does ionisation energy increase or decrease down the group?
First IE decreases down the group as extra shells are added which increases shielding and atomic radius. This reduces attraction between electron and nucleus and so are easier to remove. Overrides increase in proton.
Does melting point increase or decrease down the group?
Generally decrease down the group. Group 2 have metallic structures which are positive ions in a crystal structure surrounded by delocalised electrons. Going down the group, size of metal ion increases but number of delocalised electrons and large (+2) remains. Larger ions means distance between positive nuclei and delocalised electrons is greater - weakens attractive force.
Why is magnesium an outlier in its boiling point?
Has a different crystal structure (arrangement of metallic ions)
Does reactivity increase or decrease down the group?
Increases down the group. Atomic radius and shielding weakens attraction to nucleus so electrons loss easily.
What does group 2 react with water to make?
Bases
When group 2 reacts with water, are they oxidised or reduced?
Oxidised to make 2+ oxidation state.
What is the overall equation when group 2 reacts with water with the metal represented as ‘M’?
M (s) + 2H2O (l) –> M(OH)2 (aq) + H2 (g)
What is the reactivity of each group 2 in water?
Be - doesn’t react Mg - very slow Ca - Steadily Sr - fairly quickly Ba - rapidly
How do speed up the Mg reaction with water? What is the equation?
Using steam as it provides more energy and produces a bright white flame and white powder. Mg + H20 –> MgO + H2
What is the trend in solubility of hydroxides?
Hydroxide solubility increases down the group
Hydroxide solubility in each group 2 element
Mg - least soluble Ca Sr Ba - most soluble
Why is Mg(OH)2 known as due to its insolubility?
Sparingly soluble
What is the trend in solubility of sulfates?
Sulfate solubility decreases down the group
Sulfate solubility in each group 2 element
Mg - Most soluble Ca Sr Ba - Least soluble BaSO4 is insoluble
How to test for sulphate ions
Add dilute HCl to remove any interfering ions (like carbonate) which could give a falso result. Add barium chloride. If present, a white precipitate is formed. Ba (aq) + SO4 (aq) –> BaSO4
What is Ca(OH)2 used for?
Neutralising acid in soils.
What is Mg(OH)2 used for?
In indigestion tablets as an antacid - neutralising excess stomach acid.
Equation used in both antacids and neutralising soil?
H+ (aq) + OH- (aq) –> H2O (l)
How do barium meals work?
Barium is consumed in meals and the suspension coats soft tissue in the body. Barium sulphate is opaque to x rays and so shows up on the machine
What is the danger with barium? Why isn’t this a risk?
Barium is toxic. Barium is insoluble so doesn’t get absorbed into the blood stream.
What is the process of extracting titanium?
1) Titanium ore (TiO2) is heated with carbon and chlorine as to make titanium chloride (TiCl4). 2) TiCl4 is passed through fractional distillation column to increase purity. 3) Purified TiCl4 is reduced using magnesium in a 1000C furnace
Overall titanium extraction equation
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO TiCl4 (g) + 2Mg (l) –> Ti (s) + 2MgCl2
What is the reducing agent in titanium extraction?
Mg