≫3.2 - Group 2 Metals ✔ Flashcards
Explain the trend of atomic radius down group 2:
- Atomic radius of group 2 metals increases down the group due to additional electron shells so more shielding thus a weaker electrostatic attraction.
Explain the trend of reactivity down group 2:
- Increases down the group.
- Atoms loose electrons more readily as there is a weaker attraction between the nucleus and outer electron shell.
- Outer shell electrons are further from the nucleus due to a greater atomic radius.
- There is extra electron shielding.
Explain the trend of first ionisation energy down group 2:
- Decreases down the group.
- Increased atomic radius.
- Increased electron shielding.
- Despite increased nuclear charge there is less energy needed to remove outermost electron.
Explain the trend of melting point down group 2:
- Decreases down the group.
- Number of delocalised electrons remain the same as they all loose 2 electrons.
- Atomic radius increases
down the group. - The attraction between the ion and delocalised electrons decreases.
Give the equation for the reaction of group 2 metals with cold water:
(e.g: Mg)
- Mg + 2H₂O → Mg(OH)₂ + H₂
Describe the differences in reactions with a group 2 metal with cold water, and a group 2 metal with steam:
(e.g: Mg)
- Magnesium reacts very slowly with liquid water.
- However the reaction can be much faster with steam as it provides extra energy.
- When steam is used the magnesium burns with a bright white flame.
Give the equation for the reaction of group 2 metals with steam:
(e.g: Mg)
- Mg + H₂O → MgO + H₂
Describe the solubility of group 2 hydroxides down the group:
- The solubility of group 2 hydroxides increases down the group meaning magnesium hydroxide is the least soluble and barium hydroxide is the most soluble.
Why is magnesium hydroxide said to be sparingly soluble?
- Magnesium hydroxide is said to be sparingly soluble as the solution is slightly alkaline indicating that some hydroxide ions are dissolved in the water.
How is magnesium hydroxide used in medicine?
- Used in medicine as an antacid as it is alkaline and can neutralise acids.
How is calcium hydroxide used in agriculture and what’s it called?
- Slaked lime.
- Calcium hydroxide is used to neutralise acidic soil, the pH of soil effects its physical chemical and biological properties which in turn effects crop yield.
Describe the solubility of group 2 sulfates down the group:
- The solubility of group 2 sulfates decreases down the group meaning magnesium sulfate is the most soluble and barium sulfate is the least soluble.
How is barium sulfate used in medicine?
- The insolubility of barium sulfate means it is very useful in medicine as barium meals.
- These are a form of medical tracer that allow internal tissues and organs to be imaged as they appear on an x-ray.
- Barium sulfate is toxic if it enters the bloodstream, however because its insoluble it cannot be absorbed into the blood and therefore is safe.
What is the solubility of barium sulfate?
- Insoluble.
Describe how to test for sulfate ions:
- Dissolve a spatula of sulfate ions in dilute nitric acid solution (removes any ions that may form a ppt this causing a false positive) and then add a few cm³ of BaCl₂ solution.
- A white ppt forms which is barium sulfate.
