Group 2

• The elements of group 2 are also known as the alkali earth metals
• the oxides and hydroxides of group 2 elements are alkaline
• group 2 elements are s block elements
• group 2 elements react in a similar way to group 1 elements, but are less reactive
• the chemistry of Beryllium is atypical, so isn't considered
• group 2 elements must lose their two outer electrons and become a 2+ ion to gain a full outer shell
• Going down group 2, the highest energy electrons are held further out from the nucleus
• the group 2 elements increase in size going down the group because each element going down has an additional filled electron shell
• group 2 elements are all metals and therefore form metallic bonds and exist as giant metallic structures. In general this means group 2 elements have high melting points
• descending group 2 the ions get bigger, meaning the attraction between the sea of delocalised electrons and metal ions is weaker and therefore the metallic bonds are weaker descending the group and so the melting point decreases
• magnesium is an anomaly in terms of melting point. it has the lowest melting point of group 2, for no straight forward reason
• in all reactions concerning group 2 elements, they always lose two electrons to form a 2+ ion, meaning enough energy to cause the first and second ionisation of group 2 is needed
• Both second and first ionisation energies decrease going down group 2 because the outer most electrons are held increasingly further away and so less energy is needed to overcome the attraction between the nucleus and the outer two electrons
• Oxidation is classified as the loss of electrons. Group 2 elements are always oxidised when they take part in reactions
• All group 2 elements react with this equation with water at room temperature (M representing any group 2 element) : M (s) + 2H2O (l) → M(OH)2 (aq) + H2 (g)
• the reactivity of group 2 elements increase going down the group meaning the reactions with water become more violent as the group is descended
• Magnesium hydroxide is also called 'Milk of Magnesia' and is used as an indigestion remedy to neutralise stomach acid
• Group 2 elements react more vigorously with steam than with cold water
• Group 2 elements react with this equation with steam (M representing any group 2 element): M (s) + H2O → MgO (s) + H2 (g)
• Magnesium reacting with cold water is a very slow reaction. It can take hours for hydrogen bubbles to start to show
• Solubility of group 2 hydroxides increases down the group
• Solubility of group 2 sulfates decreases going down group 2
• Magnesium hydroxide Mg(OH)2 is insoluble
• Calcium hydroxide Ca(OH)2 is sparingly soluble
• Strontium hydroxide Sr(OH)2 is fairly soluble
• Barium hydroxide Ba(OH)2 completely dissolves
• Magnesium sulfate MgSO4 completely dissolves
• Calcium sulfate CaSO4 is fairly soluble
• Strontium sulfate SrSO4 is sparingly soluble
• Barium sulfate BaSO4 is insoluble
• X-rays are a good way at imaging the skeleton, but not so great at internal organs and soft tissue, because the x-rays pass through these structures
• Barium sulfate is very good at absorbing x-rays so is used in a 'barium meal' is given to patients to visualise their digestive system
• Barium sulfate is highly toxic but is safe to feed patients since it is so insoluble it cannot dissolve and pass through cell membranes into body tissue
• Because barium sulfate is so insoluble, the moment it is formed in a chemical reaction a white precipitate will form in the mixture. This observation can be used to test for the presence of sulfate ions
• If you have an unknown substance in a beaker, a solution of barium chloride can be added. If a white precipitate forms, sulfate ions are present
• Magnesium burns with a bright white flame
• All group 2 hydroxides appear as white precipitates when not soluble
• Calcium hydroxide is used in agriculture to neutralise acidic soils
• Titanium is a very useful metal because it is abundant, has a low density and is corrosion resistant - it is used for making light, strong alloys
• Titanium is extracted by a reaction with a more reactive metal, like magnesium