Unit 3.3 - P-Block (physics&mathstutor) Flashcards
what is amphoteric behaviour
a species which can act both as an acid and a base
which 2 p-block elements show amphoteric behaviour
Al/Al3+
Pb/Pb2+
lead oxide + hydrochloric acid
PbO + 2HCL –> PbCl₂ + H₂O
lead oxide + sodium hydroxide
PbO + NaOH + H₂O –> NaPb(OH)₃
What is inert pair effect
Tendency of S² electrons to stay paired (remain inert)
and form lower oxidation states
what is inert pair effect used to explain
That the increasing stability of the oxidation that are 2 less than group number
how does the stability of oxidation states change down group 3
stability of +1 oxidation state increases down group
how does the stability of oxidation states change down group 4
stability of +4 oxidation state decreases down the group
stability of +2 oxidation state increases down the group
how does the stability of oxidation states change down group 5
stability of +5 oxidation state decreases down group
stability of +3 oxidation state increases down the group
what is the bonding like in Al₂Cl₆ (aluminium hexachloride)
-It is a donor-acceptor dimer.
-Made of 2 separate identical molecules which are linked by 2 coordinate bonds
-2 chlorine atoms share their lone pair of electrons with 2 atoms of aluminium = coordinate bonds
what is the bonding like in NH₃BF₃
(ammonia boron trifluoride)
-it is a donor-acceptor
-coordinate bond formed between N and B atoms.
-nitrogen supplies both electrons for the covalent bond
describe structure of cubic boron nitrate
-alternately linked boron and nitrogen atoms
-structure is a tetrahedral bond network(like C in diamond)
-lone pair of electrons on N are accepted by B = giant 3D covalent lattice
describe structure of hexagonal boron nitrate
-layered structure(like graphite)
-layers form 2D giant covalent network
-alternate boron and nitrogen atoms link = hexagonal rings (thin layers) held by WEAK IMF
why is boron nitrate a good lubricant
hexagonal boron nitrate has WEAK IMF ∴ layers can slide
what is the general acid-base behaviour trend of group 4 oxides
acidity decreases as you go down group
don’t completely lose acidity(∴amphoteric)
