Group 2 Flashcards
Trends going down the group
- Atomic radii increases
- more shielding
- outer electrons further away from the nucleus
Melting point trend down the group
- Decreases due to atomic radii increase
- distance between delocalised electrons and nucleus increases
- Weaker elctrostatic forces
Reactivity trend down the group
- Increases as you move down the group
- I.E decreases
- atomic radius increases
- Number of shells increases, more shielding
- Decrease in attraction between outer electrons and nucleus
Group 2 metal + water equation
X + 2H2O –> X(OH)2 (aq/s) + H2
Group 2 metals with water
The hydroxides become more soluble as you move down the group - water is the oxidising agent
Magnisium and steam produce a white flame and white solid.
Solubility of hydroxides
- Magnisium - insoluble, pH 9 Light purple
- Calcium - Sparingly soluble, pH 11 Purple
- Barium - Soluble, pH 13
Magnesium hydroxide
Magnisium hydroxide is used in medicine (in suspension as milk of magnesia) to neutralise excess acid in the stomach and to treat constipation
Calcium hydroxide
- Partially soluble
- Used in agricluture to neutralise acidic soils
- As Lime water to test for CO2
Solubility of Sulphates
Group 2 sulphates become less soluble as you move down the group, BaSO4 is the least soluble.
Barium meal
Used as medicine to x-ray intestines. The barium absorbs the x-rays and so the gut shows up on the x-ray image. Even though it is toxic it is toxic its low solubility means it is not absorbed into the blood
Test for sulphate
- Add acidified BaCl2
- A white ppt will form if sulphate is present
- Ba2+ + SO4 2- –> BaSO4
Use of magnesium
To extract titanium
Magnesium acts as the reducing agent
Use of Calcium oxide
-
To remove SO2 from the waste gases from furnaces (e.g coal fired power stations) by fuel gas desulfurisation
The gases pass through a scrubber containing basic calcium oxide which reacts with the acidic sulfur dioxide in a neutralisation reaction
Redox
where reduction and oxidation take place in the same reaction
