3.2.2 Group 2, the alkaline earth metals Flashcards
Atomic radius trend for group 2
Increases down despite larger proton number due to more shielding, outer electrons are attracted less, so held further.
First ionisation energy trend for group 2
Decreases down the group due to shielding, resulting in weakly attracted electrons that are easily removed
Melting point trend for group 2
Generally decreases down the group (except Mg) as increased atomic radius, so the attraction between the nucleus and delocalised electrons is less.
Group 2 metals + water
Metal hydroxide (alkaline solution) + hydrogen
Mg + steam equation (+observations)
Mg(s) + H2O(l) –> MgO(s) + H2(g)
Bright white light, white solid formed
Extraction of Ti equation
2Mg + TiCl4 –> 2MgCl2 + Ti
Most and least soluble group 2 hydroxides
Most - Ba(OH)2
Least - Mg(OH)2
Use of Magnesium hydroxide
Indigestion relief
Use of Ca(OH)2
Agriculture. Neutralise acidic soil, to maintain soil quality
Flue gas desulfurisation equations
- CaO + SO2 + 1/2 O2 –> CaSO4
- CaCO3 + SO2 + 1/2 O2 –> CaSO4 + CO2
Most and least soluble sulfate in group 2
Most - MgSO4
Least - BaSO4
Use of BaSO4
Medicine. Barium meals (x-rays)
Test for sulfate ions and equation
Add dilute HCl
Add BaCl2
White ppt indicates sulfate
XSO4 + BaCl2 –> BaSO4 + XCl2
Why is dilute HCl added to test for sulfates
React with any carbonate ions that could interfere with the test
Why is BaCl2 used to test for sulfates
BaCl2 is insoluble in water so will form a ppt
