GROUP 2 Flashcards
What is the trend with the atomic radius as you go down group 2? Explain:
Atomic radius increases
Because extra electron shells are added –> more shielding
What is the trend with the first ionisation energy as you go down group 2? Explain:
It decreases
Because each element down group 2 has an extra electron shell compared to the one above, the extra shielding of the electrons from the nucleus means that they are further away from the nucleus. Reduces nuclear attraction. So, easier to remove outer electrons
What is the trend with the reactivity as you go down group 2? Explain:
REACTIVITY INCREASES
When they react they form 2+ ions. The easier it is to lose electrons
(the lower the first ionisation energy) the MORE REACTIVE
What is the trend with the melting point as you go down group 2? Explain:
Generally decrease down the group
The larger the ionic radius the further away the delocalised electrons are from the positive nuclei so less energy required to break the bonds
Which element causes the trend of the melting point to change and why?
There is a big ‘blip’ at magnesium because the crystal structure changes
Describe the structure of the metallic structure of group 2 ions:
Group 2 elements have typical metallic structures with positive ions in a crystal structure surrounded by delocalised electrons from the outer shell electrons
What happens when alkaline earth metals (group2) react?
They are oxidised from an oxidation state of 0 to an oxidation state of +2
e.g Ca –> Ca2+ +2e-
Give an equation when group 2 metals react with water, use calcium as an example:
Ca(s) + 2H2O(l) –> Ca(OH)2 (aq) + H2(g)
Group 2 hydroxide solubility trend?
increases
Group 2 sulphate solubility trend?
decreases
Why can barium sulphate be used for a barium meal even though solutiions containing barium ions are poisonous?
Because it is completely insoluble
What is magnesium hydroxide said to be in terms of solubility (Mg(OH)2)?
Magnesium hydroxide is said to be sparingly soluble
Formula for barium sulphate?
Ba(SO4)
What is the test for sulphate ions? What represents a positive result?
Add dilute hydrochloric acid and then barium chloride (BaCl2) solution to a solution containing sulphate ions, then a white ppt of barium sulphate is formed
How does a barium meal work?
The patient has a suspension containing barium sulphate, which coats the soft tissue so that it shows up on the X-rays, showing the structure of the organs.
Give the equation of how magnesium is used in the extraction of Ti from TiCl4:
TiCl4(g) + 2Mg(l) –> Ti(s) + 2MgCl2(l)
What do we used to test for sulphate ions?
Acidified barium chloride
Why do we have to remove sulphur dioxide from flue gases?
Pollutes the air –> Acid rain
Describe the process of wet scrubbing?
Where the acidic sulphur dioxide can be removed from the flue gases by reacting with an alkali. Slurry is sprayed onto the flue gases.
What two alkalis can be used during ‘wet scrubbing’?
Calcium oxide CaO LIME
Calcium carbonate CaCO3 LIMESTONE
What is the slurry made of in wet scrubbing?
A mixture of either CaO/CaCO3 and water
What is the solid waste product that is produced during wet scrubbing?
Calcium sulphite
Equation for removal of SO2 from flue gases using CaO?
CaO(s) + 2H2O(l) + SO2(g) –> CaSO3(s) + 2H2O(l)
Equation for removal of SO2 from flue gases using CaSO3?
CaO(s) + 2H2O(l) + SO2(g) –> CaSO3(s) + 2H2O(l) + CO2(g)
What is Ca(OH)2 also known as and what is used in?
AKA slaked lime
Used in agriculture to neutralise acidic soils
What is Mg(OH)2 used in?
Used in some indigestion tablets, as an ‘antacid’
What is an antacid?
A substance that neutralises excess stomach acid
Why do you need to acidify the barium chloride for the test for sulfate ions?
To get rid of any sulfites or carbonates as they will also produce a white ppt
Why can you not use sulphuric acid to acdifiy the BaCl2 for the test for sulphate ions?
It will add extra sulphate ions
What colour are group 2 hydroxides and sulfates when solid?
WHITE
