8.1 Group 2
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What are elements in group 2 of the periodic table called?
alkaline earth metals
Which electrons do alkaline earth metals lose when they react?
ns2 + ns1
Why are group 2 metals good reducing agents?
due to their ability to donate electrons
Down the group, how does the reducing power of group 2 change and why?
more powerful reducing agents: * more shells * greater shielding effect * weaker electrostatic attraction of outer electrons * electrons lost/donated more easily
What are the redox reactions of group 2?
+ O2 ⟶ metal oxide + H2O ⟶ metal hydroxide + H2 + (dilute) ACID ⟶ salt + H2
metal + oxygen ⟶
metal oxide
metal + water ⟶
metal hydroxide + hydrogen
metal + dilute acid ⟶
salt + hydrogen
Down the group, how does ionisation energy, reactivity, and reducing power of group 2 metals change?
ionisation energy less endothermic - greater shielding reactivity ￪ - electrons lost more easily reducing power ￪ - these electrons are donated
Explain how the solubility of metal hydroxides changes down the group:
Solubility ￪ down group: * more shells * larger atomic radius * weaker electrostatic attraction between oppositely charged ions * less energy required to break ionic bonds
Explain how the pH of hydroxides changes down the group:
pH ￪ down group: * Solubility ￪ * concentration of OH ￪
Metal hydroxides with a higher _____ form more alkaline solutions.
solubility
How do you test the solubility of metal hydroxides?
• mix group 2 hydroxide + water • shake • measure pH using universal indicator • repeat using different metal hydroxides
What are the uses of group 2 metal hydroxides?
INCREASE pH OF ACIDIC SOIL ANTACIDS
How can group 2 metal hydroxides be used to increase the pH of soil?
Ca(OH)2 added neutralises acids by reacting with H+
How can group 2 metal oxides be used as antacids?
Mg(OH)2 ingested neutralises some HCl
Why are specific metal hydroxides used for antacids + neutralising soil?
different metal hydroxides have different solubilities (increases down group) therefore some are more alkaline than others must choose suitable metal hydroxide for job
Which metal hydroxide is usually used for antacids?
Mg(OH)2
Which metal hydroxide is usually used for neutralising acidic soils?
Ca(OH)2