4.1 Flashcards
what does a group 2 element look like
when pure a bright silvery solid
exposed in air it appears dull as it combines with oxygen
what is the trend in ionization energy of group 2 metals
decreases down the group
why does ionization energy decrease down group 2
each quantum shell added energy of outermost electron increases
atomic radius increases so weaker force from nuclei increased shielding
what is the trend in group 2 elements for reactivity and why
increases down the group as less energy is needed to remove an electron
what would be observed if you burn magnesium in air
bright flame
formation of a white solid
how is barium often stored and why
under oil
so it cannot react with oxygen or water vapor as it is extremly reactive
what is the general equation for group 2 metals reacting with oxygen
2M(s) + O2(g) -> 2MO(s)
as you go down group 2 you can tell reactivity increases as they react with water because…
increasing effervescence
what is the general equation for the reaction of a group 2 metal with water
M(s) + 2H2O(l) -> M(OH)4(aq) + H2(g)
what is the trend in solubility of group 2
increases down the group
what is the trend in alkalinity of solutions formed of group 2
increases down the group
why does the trend in alkalinity of solutions formed of group 2 increase down the group
higher solubility therefor more OH- ions present in solution
what is the test for carbon dioxide
limewater goes cloudy
white precipitate formed
what do all group 2 oxides & hydroxides form when they react with acids
salt & water
what is the trend in solubility of group 2 sulfates
decreases down the group
what is the test for the presence of sulfate ions in an aqueous solution
add dilute nitric acid or hydrochloric acid
add solution containing barium ions
white precipitate barium sulfate formed
why are dilute nitric acid or hydrochloric acid added in the test for sulfate ions
to prevent barium carbonate from forming as a white precipitate
what is thermal stability
measure of the extent to which a compound decomposes when heated
why do group 2 nitrated & carbonates have lower thermal stability than group 1
cation charge greater than group 1 therefor group 1 ions are less polarising so need more heating tham group 2
what happens to group 2 nitrates & carbonates when they are heated
they decompose
what do all nitrates of group 1 and 2 look like
white solid
what is observed when group 1/2 nitrates decompose
decompose to nitrites or oxides
nitrogen dioxide (brown gas) is produced
what do all group 1/2 carbonates look like
white solids
what happens to group 1 & 2 carbonates when they are heated
don’t decompose
or
decompose to oxides and give off carbon dioxide
what are the problems with flame tests
many compounds contain sodium impurities which will mask other colours
subjective to different levels of colour vision
what is the flame test for lithium Li+
red
what is the flame test for sodium Na+
yellow/orange
what is the flame test for potassium K+
lilac
what is the flame test for rubidium Rb+
red/purple
what is the flame test for caesium Cs+
blue/violet
what is the flame test for beryllium Be2+
no colour
what is the flame test for calcium Ca2+
brick red
what is the flame test for magnesium Mg2+
no colour
what is the flame test for strontium Sr2+
crimson red
what is the flame test for barium Ba2+
(apple) green
what is the flame test for copper
blue/green
what is the test for aqueous ammonium ions
add sodium hydroxide solution & warm
ammonia gas produced
