Topic 4: Inorganic Chemistry and the Periodic Table Flashcards
What are the trends in ionisation energy down Group 2?
I.E decreases: increase in atomic radius and shielding increases.
Outweigh the increase in proton number.
What are the trend in reactivity down group 2?
Reactivity increases as easier to remove the two electrons from the outermost shell.
Covalent or Ionic Compound when Group 2 reacts with Chlorine?
All are ionic compounds but
BeCl2 (anhydrous) is covalent
Group 2 reactions with water
Beryllium does not react with water
Magnesium reacts v. v. slowly with steam to produce MgO + H2
Others react to form hydroxides
Solubility trends with Group 2 Metals
Hydroxides solubility increase down the group (increases the pH)
Sulphates solubility decreases down the group
Thermal stability of Group 2 compared to Group 1
Group 2 carbonates are less stable because Group 1 have larger ionic radius + smaller charge. So it’s less polarising and polarises the electron cloud of carbonate/nitrate ion less.
Trend in thermal stability of carbonates and nitrates in Group 2
Polarising power decreases down Group 2 as ionic radius increases.
Carbonate/nitrate ion is less distorted and less polarised so C-O/ N-O bond not weakened as much.
So Group 2 carbonates/nitrates decompose with increasing difficulty down the group
Carbonates/nitrates become more stable down the group
Decomposition of Group 2 Nitrates
Magnesium Nitrate –> Magnesium oxide + nitrogen dioxide (brown fumes) + oxygen
Decomposition of Group 1 Nitrates
Rest:
Sodium Nitrate –> Sodium Nitrite + Oxygen (no brown fumes)
Lithium:
Lithium nitrate –> Lithium oxide (Li2O) + Nitrogen dioxide + Oxygen
(Brown fumes)
Flame Colours of Group 1 and Group 2:
Lithium ion
Sodium ion
Potassium ion
Calcium ion
Strontium ion
Barium ion
Copper (II) ion
Li = Red
Na = Yellow
K = Lilac
Ca = yellow-red
St = red
Ba = pale green
Cu = Blue-green
Flame Test procedure
Dip nichrome wire into HCl then the salt
Put the nichrome wire in the blue flame and observe the colour
Physical Trends of Group 7 down the group
Physical state increases from gas to solid
Colour darkens
Melting and boiling point increases down the group as strength of LF increases
Electronegativity decreases as atomic radius increases down the group, reducing attraction of nucleus and shared pair of electrons
Trend for reactivity down Group 7
Reactivity decreases down the group
Increasing atomic radius
Harder to attract 1 electron to the outer shell as attraction from nucleus weaker
Disproportionation Reactions Group 7
When an element in a single specie is both oxidised and reduced
Chlorine disproportionates in water (-1 & +1)
Chlorine disproportionates in cold alkali (-1 & +1)
Chlorine disproportionates in hot alkali (-1 & +5)
[bromine and iodine the same but in lower temps]
Reactions of Group 1 halides with conc sulphuric acid
Produced hydrogen halide
May reduce further with conc sulphuric acid (excess)
Dependent on reducing ability of the halogen (increases down the group)
