8.1 Group 2

describe how group 2 elements are reducing agents

in redox reactions each group 2 metal atom is oxidised, losing two electrons to form a 2+ ion and reducing another species

group 2 element + water

alkaline hydroxide M(OH)₂ + H₂

does reactivity increase or decrease down group 2

increase

metal + acid

salt + hydrogen

why does reactivity increase down group 2

1) group 2 elements react by losing two electrons to form 2+ ions

2) the ionisation energies decrease down the group because of increasing atomic radius and increasing shielding = weaker attraction of outer electrons to the nucleus = outer electrons are more easily removed

3) therefore the group 2 elements become more reactive + stronger reducing agents down the group

group 2 metal oxide + water

metal hydroxide

does the solubility of group 2 hydroxides in water increase or decrease down the group and why

increases with increasing hydroxide ion concentration and increasing pH

how to test the trend of solubility of group 2 hydroxides in water

1) add a spatula of each group 2 oxide to water in a test tube

2) shake the mixture to form a saturated solution of each metal hydroxide with some undissolved white solid at the bottom of the test tube

3) measure the pH. alkalinity increases

describe the use of calcium hydroxide in agriculture

added to fields as lime by farmers to increase the pH of acidic soils, forming neutral water

Ca(OH)₂ (s) + 2H⁺(aq) → Ca²⁺(aq) + 2H₂O(l)

uses of Mg(OH)₂ in medicine

antacids for treating acid indigestion

milk of magnesia

Mg(OH)₂(s) + 2HCl(aq) → MgCl₂ (aq) + 2H₂O (l)