Groups 1, 2 Flashcards
name the three physical properties of group two elements
- ionisation energy
- atomic radius
- reactivity
how does ionisation energy change down group two and why
- ionisation energy decreases down group two
- greater atomic radius, increased shielding, easier to lose an electron
how does reactivity change down group two and why
- reactivity increases down group two
- increased electron shielding and atomic radius, outer (valence) electron easier to lose, reactions can occur more easily
how does atomic radius change down group two and why
- atomic radius increases
- additional electron shells
what type of reaction is a metal + water
redox reaction
metal + water ->
metal hydroxide + hydrogen
what kind of solution is a metal hydroxide
an alkaline solution
general equation for reaction of group 2 metals with water
M(s) + 2H2O(l) -> M(OH)2(aq) + H2(g)
how is a reaction with water different to one with steam
- steam produces a metal oxide and hydrogen
- reaction with steam is faster because it has more energy
metal + steam ->
metal oxide (white powder) + hydrogen
general equation for reaction of group 2 metal and steam
M(s) + H2O(g) -> MO(s) + H2
metal + chlorine gas ->
metal chloride (white precipitate)
general equation for reaction of group 2 metal + chlorine gas
M(s) + Cl2(g) -> MCl2(s)
how does reactions with chlorine gas change down group two
- it becomes more vigorous down group 2
- because metals more reactive
metal + oxygen ->
metal oxide
general equation for group 2 metal + oxygen in normal conditions
2M(s) + O2(g) -> 2MO(s)
which two group two metals dont fit the general pattern of reaction with oxygen
strontium and barium
strontium/barium + oxygen ->
metal peroxide
when do strontium and barium become peroxides
when reacting with excess oxygen and heat energy
(with excess oxygen and heat energy)
M(s) + O2(g) ->
MO2
which group 2 metals react
Mg-Ba
general equation for reactions of metal oxides and water
MO(s) + H2O(l) -> M(OH)2(aq)
general equation for reactions of metal oxides and dilute hydrochloric acid
MO(s) + 2HCl(aq) -> MCl2(aq) + H2O(l)
general equations for metal hydroxides in water
—————H2O(l)——————
M(OH)2(s) ——-> M(OH)2(aq)
general equation for reactions of metal hydroxides and dilute hydrochloric acid
M(OH)2(aq) + 2HCl(aq) –> MCl2(aq) + 2H2O(l)
how does solubility of metal hydroxides change down group two
- solubility increases down group two
- (magnesium hydroxide least soluble)
real life uses of magnesium hydroxide
- antiacid (neutralises acids in the body)
- neutralises acidic soil
how does solubility of metal sulfates change down group two
- solubility decreases down group two
- (barium sulfate least soluble)
real life uses of barium sulfate
- used in medicine as ‘barium metals’ (allows internal organs and tissues to be imaged)
- usually toxic, but cannot be absorbed into the bloodstream so safe
how does thermal decomposition occur
when substances are heated in aerobic conditions
thermal decomposition of a group 2 metal carbonate produces
metal oxide (white powder) + carbon dioxide
general equation for thermal decomposition of group 2 metal carbonates
MCO3(s) –> MO(s) + CO2(g)
group 2 metal nitrates undergo thermal decomposition to form
metal oxide + nitrogen dioxide + oxygen
general equation for thermal decomposition of group 2 metal nitrates
2M(NO3)2(s) —> 2MO(s) + 4NO2)g) + O2(g)
what group 1 metal carbonate and nitrate acts the same as group 2
lithium
thermal decomposition of group 1 metal carbonates
- wont decompose upon heating as they require extremely high temperatures to do so
group 1 metal nitrates undergo thermal decomposition to produce
metal nitrite + oxygen
general equation for thermal decomposition of group one metal nitrates (excluding lithium)
2MNO3(s) –> 2MNO2(s) + O2(g)
describe and explain the trend in thermal stability for group 1 and 2 nitrates and carbonates
- become more thermal stable down the group
- down group, ionic radius increases (-smaller ions at top have a higher charge density)
- higher charge density
- polarise more
- distorts anion
- weakens c-o bond /n-o bond
- less thermally stable
