3.2.2 Group 2, the alkaline earth metals Flashcards
What happens to the atomic radius of group 2 metals as we go down the group and why?
Atomic Radius increases
More electron shells added, increased shielding
Nuclear charge increases but ouutweighed by increased distance and shielding.
Definition of first ionisation energy
Energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
What happens to first ionisation energy as we move down group 2?
Increases, extra shells added, more shielding and weaker attraction between the nucleus and outermost electron. Proton number also increases but shielding overrides this. Therefore, less energy is required to remove those outermost electrons.
What is the general trend in melting points down group 2?
Decreases, down the group size of metal ion increases but the number of delocalised electrons remains the same. Distance between positive nuclei and delocalised electrons increases, attractive forces weaken making it easier to loosen metallic bonds.
Group 2 metals burn in oxygen, what observation can be made with this reaction : 2Mg + O2 = 2MgO
Mg burns with a brigh white flame.
What happens to reactivity down group 2
Increases
Mg reacts with steam to produce…
Magnesium oxide and hydrogen
Observations of Mg reacting with steam
Bright white flame/light
Mg reacts with cold water to produce…
Magnesium hydroxide and hydrogen
Observation when Mg reacts with warm water
Much slower reaction than the reaction with steam
No flame
What is generally produced when group 2 metals react with water?
Metal Hydroxides
List observations of the reaction of group 2 metals and water.
- Fizzing
- Metal dissolving
- Solution heats up
- Calcium produces a white ppt
Why is titanium used in aircrafts, for example?
Low density and corrosion resistant
What metal is used to extract titanium from its ore (rutile)?
Magnesium
Describe the process of extracting Titanium from its ore.
- Titanium is converted to TiCl4
- TiCl4 is passed through a fractional distillation column - to increase its purity
- Purified TiCl4 is reduced using Mg in a 1000 degree furnace
What is the equation for the extraction of titanoum from titanium chloride using magnesium?
TiCl4 + 2Mg = Ti +2MgCl2
Describe the trend in solubility of Group 2 hydroxides.
Increases down the group
(More soluble down the group)
What is the use for the sparingly soluble Magnesium Hydroxide?
Used to neutralise excess stomach acid
(antacid)
What is the use for the slightly soluble Calcium Hydroxide?
Used to neutralise acidic soils
What can be tested for using an aqueous solution of calcium hydroxide (lime water) and what is the positive result?
Carbon dioxide
Solution will turn cloudy, white calcium carbonate is produced
What is the solubility trend for group 2 sulfates?
Solubility decreases down the group.
What is the use of the sparingly soluble Barium sulfate?
Barium meal
Absorbs X-rays to identify problems with digestive tract
Why is barium sulfate safe to use despite its toxicity?
Low solubilty = not absorbed in the blood
What is the use of CaO or CaCO3?
Neutralises and removes sulfur dioxide in flue gases via a process called wet scrubbing.
