reactivity trends

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reactivity trends

group 2:

they are alkaline earth metals

alkaline are used to neutralise things that are acidic, and are able to be consumed as they are not very strong

some uses include: neutralise soils, helps with stomach indigestion, detergent, toothpaste etc.

group 2 alkaline are not as strong as group 1 alkaline as they are less soluble (the more soluble the element, the more alkaline it is)

down the group the alkaline becomes more soluble and therefore the alkaline gets stronger / more OH- ions are attracted when more soluble and thats why the alkali becomes stronger

going down pH increases

reactivity trend in group 2 -

easier to lose 2 outer e-

extra shell, radius gets bigger

greater shielding

shielding outweighs the extra nuclear charge

nuclear attraction decreases

redox -

in a redox reaction, group 2 elements are oxidised by losing 2 e- to form a 2+ ion. It is also called a reducing agent as another element will gain these 2 e- and be reduced

reactions -

group 2 metal + oxygen > metal oxide

group 2 metal + water > metal hydroxide + hydrogen

group 2 metal + acid > salt + hydrogen

metal oxide + acid > metal salt + water

metal hydroxide + acid > metal salt + water

metal carbonate + acid > metal salt + carbon dioxide + water

metal carbonate + heat > metal oxide + carbon dioxide

group 7:

down the group, boiling points increase = more e- are added = larger uneven distribution of e- = greater london forces

reactivity decreases down a group = atomic radii increases = extra shell, weaker nuclear attraction = outweighs nuclear charge = harder to gain an e-

some uses: toxic, disinfectant, kills bacteria

colours of main elements -

Chlorine = pale green

bromine = orange

iodine = brown + cyclohexane = violet

redox -

chlorine is a good oxidising agent, it is good at attracting e-, gaining the e- means it is being reduced, taking it away from another element and that element is oxidised

test for halide ions -

when silver nitrate is added to any substance containing halide ions

Chlorine ions will form a white precipitate (dissolves in dilute ammonia NH3)

Bromine ions form a cream precipitate (dissolves in concentrated ammonia)

Iodine ions form a yellow precipitate (does not dissolve)

Disproportionation:

an element that is both oxidised and reduced simultaneously (eg. Cl with water)

Qualitative analysis:

anion test -

add dilute nitric acid, then pass the carbon dioxide gas through limewater which will turn cloudy if a carbonate ion is present

if not, dissolve the solution in dilute nitric acid and a white precipitate will form if barium nitrate/(barium chloride) solution is added and a sulphate ion is present

if not, dissolve in dilute nitric acid and add a silver nitrate solution. if the anions chloride, a white pp forms; if it is bromide, a cream pp forms; if it is iodine, a yellow pp forms

cation test -

to see if an ammonium ion is present, heat with sodium hydroxide solution and ammonia gas will be formed; turns red litmus paper blue and gives of a smell