Group 2 and group 7 elements

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Group 2 elements:

  • have high melting and boiling points
  • are light weight and have low densities
  • form colourless compounds

Group 2 elements are strong reducing agents, they are oxidised in reactions as they lose electrons. The oxidation state of the alkali earth metals is +2.

Reactivity increases down the group because it is easier to lose electrons as the ionisation energies decrease down the group. 

Group 2 elements react vigorously with oxygen, forming an ionic oxide with the general formula MO.

Group 2 elements react with water, forming a hydroxide and hydrogen gas.
The observations of this reaction are the solid dissolving and disappearing and fizzing due to gas production. 

Group 2 oxides and hydroxides are bases, they are neutralised by acids forming a salt and water. The observation is the solid oxide or hydroxide dissolving in the acid.

Group 2 oxides react with water, forming a metal hydroxide in solution whilst group 2 hydroxides dissolve in water forming alkaline solutions.

Solubility of the metal hydroxides increases down the group and the alkalinity of the solutions formed increase down the group, this is because the concentration oh OH- ions is higher. 

Group 2 carbonates undergo thermal decomposition, forming a metal oxide and carbon dioxide. 
The further down the group the less easily the carbonates decompose, the temperatures needed…

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