3.1.2 Group 2
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what are the elements in group 2 named sometimes
• alkaline earth metals > they are metals
where are the 2 outer shell electrons found in g2 elements
• in the outer s sub-shell
what happens to g2 elements in redox reactions
• metal atom oxidised > lose 2e- to form 2+ ion • another species gains the 2e- and is reduced
why are g2 elements reducing agents
• they cause another species to be reduced (it itself is oxidised)
what are the 3 different redox reactions g2 undergo
• oxygen • water • dilute acids
what is formed when g2 element reacts with oxygen
• metal + oxygen —> metal oxide
what is oxidised + reduced in redox reaction of g2 elements with oxygen + give oxidation number
• metal oxidises 0 —> +2 • oxygen reduces 0 —> -2
what is formed when g2 elements reacts with water
• metal + water —> metal hydroxide (alkaline) + hydrogen
what is formed when g2 elements react with dilute acid
• metal + acid —> salt + hydrogen
describe the trend in reactivity down g2
• reactivity increases down group > atomic radius inc + electron shielding inc > so nuclear attraction to outer shell electrons decrease > ionisation energy decrease > more easier to remove outer shell e- so more reactive
describe the trend in reactivity down g2
• mp/bp decrease > atomic radius inc so weaker attraction between positive nucleus and delocalised electrons > metallic bonding also weaker due to weaker imf
what happens when a g2 oxide reacts with water
• forms metal hydroxide (alkaline)
are g2 hydroxides soluble
• slightly soluble in water
describe the trend in solubility of hydroxides down g2
• solubility inc down group > releases more OH- + solution is more alkaline
why are g2 compounds useful
• they are basic so can neutralise acids
what is the use of g2 compounds in agriculture + equation
• calcium hydroxide (lime) added to fields to neutralise acid in soil / inc pH of acidic soil and forms neutral water Ca(OH)2 (s) + 2H+(aq) —> Ca2+(aq) + 2H2O(l)
what is the use of g2 compounds in medicine
• used as antacids + treat acidic indigestion • magnesium hydroxide or calcium carbonate used to neutralise excess stomach acid Mg(OH)2(s) + 2HCl(aq) —> MgCl2(aq) + 2H2O(l) CaCO3(s) + 2HCl(aq) —> CaCl2 (aq) + H2O (l) + CO2(g)