What general properties do group 2 elements have?
- They have reasonably high melting and boiling points.- They are light metals with low densities - They form colourless compounds
What orbital do the group 2 elements have their highest electrons in?
The s sub-shell.Together with group 1 they form the s-block of the periodic table.
Why does the reactivity of group 2 elements increase down the group but the ionisation energy decreases?
- The reactivity increases reflecting the increased ease in group 2 loosing electrons.- The decrease in ionisation shows the increased electron repulsion and addition of new shells.
Describe the reaction between group 2 elements and oxygen.
- It is a redox reaction, oxidation a numbers only appear on he the products.- The product is an ionic oxide with the general formula MO- The group 2 elements react vigorously with oxygen.
Describe the group 2 reaction with water.
- the group 2 elements react with water to form hydroxides with the general formula M(OH)2. Hydrogen gas is also produced.- Note that only one H atom in each H2O has been reduced.- The other H atom does not change its oxidation number.- As you move down the group, each metal reacts more vigorously with water.
What are group 2 oxides and hydroxides?
Bases
If a group 2 oxide or hydroxide were to react with HCl how would you tell when the reaction was complete?
As these reactions with HCl acid take place you will see the solid oxides or hydroxides dissolve.
What happens when the group 2 oxides react with water?
A solution of a metal hydroxide is produced.The typical pH of these solutions is 10-12.
What do group 2 hydroxides dissolve in water to produce what?
They dissolve in water to form alkaline solutions.Ca(OH)2 + aq –> Ca 2+ (aq) + 2OH-
What happens to the solubility of group 2 hydroxides down the group?
The solubility if the hydroxides in water increases down the group, the resulting solutions are more alkaline as hydroxides from further down of group 2 dissolve more in water.
What is thermal decomposition?
Thermal decomposition is the breaking up a chemical substance with heat into at least two chemical substances.
What do group 2 carbonates decompose with heat to produce?
The produce the metal oxide and carbon dioxide gas.The carbonates become more difficult to decompose with heat as you move down the group.
Why do group 2 carbonates become harder to decompose down the group?
This is because the group 2 atoms at the top of group 2 have the same ionic charge (2+) but in a more dense space as they are smaller. This means when bonding with CO3 the electrons are all attracted to the densely charged ion leaving the CO2 part of CO3 with less time around the electrons and so less energy is required to overcome the attraction.
What are the three main properties if group 2 elements down the group?
- they become more reactive down the group- the carbonates decompose at high temperatures down the group - the hydroxides become more soluble in water, and the resulting solution more alkaline down the group.
What are two common uses of group 2 hydroxides?
- Calcium hydroxide used as lime to neutralise acid soils.- magnesium hydroxide used to relieve indigestion, by reacting with excess acid in the stomach.
