M3 ,, Group 2

Question 1

Atomic radius G2?

Answer 1

Atomic radius increases down the Group.
As one goes down the group the atoms have more shells of electrons making the atom bigger

Question 2

Melting points G2

Answer 2

Melting points decrease down the group. The metallic bonding weakens as the atomic size increases. The distance between the positive ions and delocalized electrons increases. Therefore the electrostatic attractive forces between the positive ions and the delocalized electrons weaken.

Question 3

Electronic structure G2?

Answer 3

Group 2 metals all have the outer shell s2 electron configuration.

Question 4

Ionisation energy G2?

Answer 4

When the group 2 metals react, they lose their outer shell s2 electrons in redox reactions to form 2+ ions. The energy to remove these electrons are the first and second ionisation energies.

Question 5

1st and 2nd ionisation energy?

Answer 5

The first and second ionisation energies decrease down the group. The outermost electrons are held more weakly because they are successively further from the nucleus in additional shells
In addition, the outer shell electrons become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons

Question 6

Second ionisation energ?

Answer 6

The second ionisation energy is the enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge

Ti+(g) ——> Ti^2+(g) + e-

Question 7

Reactivity G2?

Answer 7

The reactivity increases down the group. As the atomic radius increase there is more shielding. The nuclear attraction decreases and it is easier to remove outer electrons. Cations form more easily.

Question 8

G2 reactions with oxygen?

Answer 8

Mg will also react slowly with oxygen without a flame.
Mg ribbon will often have a thin layer of magnesium oxide on it formed by reaction with oxygen
2Mg + O2 —> 2MgO
This needs to be cleaned off by emery paper before doing reactions with Mg ribbon

Question 9

G2 with water?

Answer 9

Magnesium reacts in steam to produce magnesium oxide and hydrogen. The Mg would burn with a bright white flame
Mg (s) + H2O (g) —> MgO (s) + H2 (g)

Mg will also react with warm water, giving a different magnesium hydroxide product
Mg + 2 H2O —> Mg(OH)2 + H2
This is a much slower reaction than the reaction with steam and there is no flame

The other group 2 metals will react with cold water with increasing vigour down the group to form hydroxides
Ca + 2 H2O (l) —>Ca(OH)2 (aq) + H2 (g)
Sr + 2 H2O (l) —> Sr(OH)2 (aq) + H2 (g)
Ba + 2 H2O (l) —> Ba(OH)2 (aq) + H2 (g)

Question 10

G2 w/ water observations?

Answer 10

fizzing, (more vigorous down group)
the metal dissolving, (faster down group)
the solution heating up (more down group)
and with calcium a white precipitate appearing (less precipitate forms down group)
Reactions with acid
If bariu

Question 11

G2 reactions with acid?

Answer 11

The group 2 metals will react with acids with increasing vigour down the group to form a salt and hydrogen
Ca + 2HCl (aq) —> CaCl2 (aq) + H2 (g)
Sr + 2 HNO3 (aq) —> Sr(NO3)2 (aq) + H2 (g)
Mg + H2SO4 (aq) —> MgSO4 (aq) + H2 (g)

Question 12

Barium metal with sulphuric acid?

Answer 12

If barium metal is reacted with sulfuric acid it will only react slowly as the insoluble barium sulfate produced will cover the surface of the metal and act as a barrier to further attack. Ba+H2SO4BaSO4 +H2
The same effect will happen to a lesser extent with metals going up the group as the solubility increases.
The same effect does not happen with other acids like hydrochloric or nitric as they form soluble group 2 salts.

Question 13

Water and Magnesium oxide?

Answer 13

Magnesium hydroxide is classed as partially soluble in water.
A suspension of magnesium hydroxide in water will appear slightly alkaline (pH 9) so some hydroxide ions must therefore have been produced by a very slight dissolving.
Magnesium hydroxide is used in medicine (in suspension as milk of magnesia) to neutralise excess acid in the stomach and to treat constipation.
Mg(OH)2 + 2HClMgCl2 + 2H2O
It is safe to use as it so weakly alkaline.

Question 14

Water and calcium hydroxide?

Answer 14

Calcium hydroxide is reasonably soluble in water. It is used in agriculture to neutralise acidic soils.
If too much calcium hydroxide is added to the soil, excess will result in soils becoming too alkaline to sustain crop growth

Question 15

Water and aqueous calcium hydroxide?

Answer 15

An aqueous solution of calcium hydroxide is called lime water and can be used a test for carbon dioxide. The limewater turns cloudy as white calcium carbonate is produced.
Ca(OH)2 (aq) + CO2 (g)  CaCO3 (s) + H2O(l)

Question 16

Group 2 and oxides?

Answer 16

The group 2 oxides react with water to form hydroxides of varying solubility