Group 2 Flashcards
What do all group 2 elements in common?
They have 2 electrons in their outer shell
What happens when group 2 elements react?
They lose 2 electrons and form 2+ ions
M(g) –> M(g)2+ + 2e-
What is the trend for the atomic radius down the group?
The atomic radius increases down the group
Why does the atomic radius increase?
There are extra electron shells as you go down the group
What is the trend for the first ionisation energy down the group?
The first ionisation energy decreases down the group
What factors cause the first ionisation energy to decrease?
- Each element down group 2 has an extra electron shell compared to the one above
- The inner shells shield the outer electrons from the attraction of the nucleus
- The outer electrons are further away from the nucleus which reduces the force of attraction
What is the trend in the reactivity down the group?
The reactivity increases down the group
Why does the reactivity increase down the group?
When the elements react, they lose electrons.
The easier it is to lose electrons, the more reactive the element
In group 2, when is it easier to lose electrons?
First and second ionisation energies
What is the general trend for melting points down the group?
The melting points generally decrease down the group
What type of structure does group 2 element have?
They have a giant metallic structure with positive ions surrounded by delocalised electrons from the outer electron shells
Why do the melting points decrease down the group?
The larger the ionic radius, the further away the delocalised electrons are from the nucleus and the lower the force of attraction.
Therefore, less energy is needed
Why is there a large drop in the melting point between beryllium and magnesium?
The metallic structure changes
What other name is given to group 2?
Alkaline Earth metals
Why is group 2 called alkaline earth metals?
Their oxides and hydroxides are alkaline
Which hydroxides are sparingly soluble?
Mg(OH)2
Ca(OH)2
Why are Mg(OH)2 and Ca(OH)2 sparingly soluble?
Their reactions with water are reversible
This means that the reactions are not complete
Why are Sr(OH)2 and Ba(OH)2 soluble in water?
These metals are more reactive than Ca and Mg
Their reactions are not reversible as they react fully
What can be observed as the metals react with water?
Down the group
- more vigorous fizzing
- faster dissolving
- the solution heats up
- less precipitation
What happens when magnesium reacts with steam?
Magnesium oxide and hydrogen are produced
Mg(s) + H20(g) → MgO(s) + H2(g)
What is the trend in the solubility of the hydroxides of group 2 elements, Mg-Ba?
The solubility increases down the group
What is the trend in the solubility of the sulfates of group 2 elements, Mg-Ba?
The solubility decreases down the group
Which sulfate is insoluble?
BaSO4
How is Mg(OH)2 used in medicine?
It is a weak alkali and used in the acid neutralisation in the stomach(indigestion)
How is BaSO4 used in medicine?
Barium meals
It is opaque and used for live x-rays to diagnose problems in the digestive system
How is Ca(OH)2 used in agriculture?
It is used in the neutralisation of the acidic soil
What is the ionic equation for the neutralisation in both cases of Ca(OH)2 and Mg(OH)2?
H+(aq) + OH-(aq) → H2O(l)
What is magnesium used to extract?
Titanium
What is the process for the extraction of titanium?
The titanium ore is converted to titanium chloride by heating it with carbon is a stream of chlorine gas
Titanium chloride is then purified by fractional distillation before being reduced by magnesium in a furnace
What is the equation for the extraction of titanium?
TiCl4(g) + 2Mg(l) → Ti(s) + 2MgCl2(l)
Why is titanium desired?
It is a very strong metal
E.g. it is used in the bodies of modern planes
How are calcium oxide and calcium carbonate used?
They are used to remove sulphur dioxide
What is wet scrubbing?
The process of removing acidic sulphur dioxide from flue gases by reacting with an alkali
What are the equations for the reaction of sulphur dioxide with calcium oxide or calcium carbonate?
CaO(s) + SO2(g) → CaSO3(s)
CaCO3(s) + SO2(g) → CaSO3(s) + CO2(g)
How would you test for sulphate ions?
Adding acidified barium chloride to a solution containing sulfate ions which would form a white precipitate of barium sulfate
Why does the barium chloride need to be acidified before added to the solution?
Acidifying the barium chloride means that any carbonates can be removed as carbonates produce white precipitates too
This would produce a false positive result
What is the ionic equation for the reaction of acidified barium chloride with the sulfate solution?
Ba(2+)(aq) + SO4(2-)(aq) → BaSO4(s)
