4A: The elements of Groups 1 and 2 Flashcards
State and explain the trend in ionisation energy down group 2.
Decreases.
Same nuclear charge,
shielding and atomic radius increases,
So attraction between the nucleus and outer electrons is weaker.
State and explain the trend in reactivity of group 2 elements down the group.
Increases.
1st and 2nd ionisation energies decrease.
Strength of metallic bonds decreases.
So reducing strength increases.
Reaction of elements in group 2 with Oxygen
2 M + O2 -> 2 MO
(Except Barium)
Reaction of Ba with Oxygen
Ba + O2 -> BaO2 (Barium peroxide)
Reaction of elements in group 2 with Chlorine
M + Cl2 -> MCl2
Reaction of elements in group 2 with Water
M + 2 H2O -> M(OH)2 + H2
Reaction of oxides of Group 2 elements with Water
MO + H2O -> M(OH)2
Reaction of oxides of Group 2 elements with Sulphuric acid
MO + H2SO4 -> MSO4 + H2O
Reaction of hydroxides of Group 2 elements with Nitric acid
M(OH)2 + 2 HNO3 -> M(NO3)2 + 2 H2O
What is the trend in solubility of the hydroxides of Group 2 elements?
More soluble down the group
Be, Mg - insoluble
Ca - slightly soluble
Sr, Ba - soluble
What is the trend in solubility of the sulfates of Group 2 elements?
Less soluble down the group
Be, Mg - soluble
Ca - slightly soluble
Sr, Ba - insoluble
State and expain the trend in thermal stability of the nitrates of elements in Groups 1 and 2.
As you go down the group,
The cation has less charge density (same charge, larger radius),
so it polarises the nitrate ion less,
so the N-O bond is weakened less,
so it is more thermally stable.
State and expain the trend in thermal stability of the carbonates of elements in Groups 1 and 2.
As you go down the group,
The cation has less charge density (same charge, larger radius),
so it polarises the carbonate ion less,
so the C-O bond is weakened less,
so it is more thermally stable.
Desribe how to perform a flame test.
Dip nichrome wire into HCl,
dip into sample,
hold sample over non-luminous blue bunsen flame,
observe flame colour.
Why is a nichrome wire used in a flame test?
Does not give a flame colour.
Why is the wire dipped into HCl before a flame test?
Cleans the wire
(+ makes it damp so the solid sticks better)
Explain the formation of characteristic flame colours by Group 1 and 2
compounds.
Electrons are pushed to a higher energy level.
As they drop back to a lower level they give out energy in the form of light.
What are the products from the decomposition of lithium and Group 2 nitrates?
Metal oxide, Nitrogen dioxide, oxygen
Li2O + 2 NO2 + 1/2 O2
MO + 2 NO2 + 1/2 O2
What are the products from the decomposition of most Group 1 nitrates?
Metal nitrate(III), oxygen
MNO2 + 1/2 O2
Describe the experimental procedure to show patterns in thermal decomposition of Group 1 and 2 carbonates
Heat the carbonate,
pass the gas through limewater,
measure how long it takes for the limewater to turn cloudy.
Describe the experimental procedure to show patterns in thermal decomposition of Group 1 and 2 nitrates
Heat the nitrate,
measure how long it takes for brown gas to form / glowing splint to relight
