A3.1 - Group 2
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What sub-shell are the outer shell electrons in down group 2?
S sub shell s2
Do elements in group 2 gain or lose electrons during redox reactions?
lose electrons form 2+ ions
What are group 2 elements called?
Alkaline earth metals
What is the most common type of reaction of group 2 metals?
redox reactions
What happens to group two metals during redox reactions?
oxidised forming 2+ ion reducing agent
Redox reactions with oxygen
• form a metal oxide • general formula MO, made up of M2+ and O2- ions • total changes in oxidation number will balance
Redox reactions with water
• form an alkaline hydroxide • general formula M(OH)2 and hydrogen gas • reactivity increases down the group
Redox reactions with dilute acids
• form a salt and hydrogen gas (MASH) • reactivity increases down the group
What is the trend in reactivity in terms of the first and second ionisation energies down the group?
• ionisation energies increase down the group • atomic radius increases • electron shielding increases • force of attraction between the nucleus and outer shell electrons decrease
What is the trend in reactivity down group 2?
• reactivity increases • form 2+ ions • requires the input of two ionisation energies
What happens when group 2 oxides react with water?
• release hydroxide ions, OH- • forming alkaline solutions of the metal hydroxides
When group 2 oxides react with water, what happens when the solution becomes saturated?
any further metal and hydroxide ions will form a solid precipitate
What is the trend of the solubility of hydroxides down group 2?
• solubility increases • pH increases • alkalinity increases
What is an experiment to show trend down group 2: tests alkalinity
• Add a spatula of each group 2 oxide to water in a test tube • Shake the mixture –> insufficient energy to dissolve all of the metal hydroxide that forms on this scale • Measure the pH of each solution –> alkalinity will be seen to INCREASE down the group
Uses of group 2 compounds: calcium hydroxide
Ca(OH)2 - added to fields s lime by farmers to increase the pH of acidic soils –> neutralise
Uses of group 2 compounds: magnesium hydroxide and calcium carbonate
Mg(OH)2 and CaCO3 used as ‘antiacids’ for treating acid indigestion