Chemistry of the p-block (DONE) Flashcards
Describe the Periodic Trend across a period in Atomic Radius.
(3 marks)
- Radius decreases from left to right across a period
- This is because the number of protons increases and shielding of electrons remains constant.
- Greater pull on outer electrons, which causes atomic radius to decrease
Describe the Periodic Trend down a group in Atomic Radius.
(2 marks)
- Atomic radius increases down a group
- Due to adding more shells of electrons
one per period
Describe the general trend in first ionisation energy across a period.
(3 marks)
- Generally increases from left to right across a period
- This is because number of protons increases and number of shielding electrons remains constant.
- Atomic radius decreases making it more difficult to remove an outer electron
Describe the general trend in first ionisation energy down a group.
(3 marks)
- IE decreases going down a group
- Outer electrons get further away from the pull of nucleus and inner shell shielding increases
- This takes priority over the number of protons increasing in the nucleus
What is electronegativity?
The ability of an atom to attract a pair of electrons from a covalent bond towards itself.
What is the inert pair effect and what groups does it apply to?
(4 marks)
- Groups 3,4 and 5
- The tendency of two electrons in the outermost atomic s-orbital to remain unshared.
- Going down the group there is increasing stability of the inert pair
- Oxidation state reduces down a group (in group 4 the stability goes from +4 to +2)
What is octet expansion?
(1 mark)
The ability of some atoms to use d-orbitals to have more than 8 electrons in their valence(outer) shell.
What does amphoteric behaviour mean?
A compound, element or ion reacts with both acids and bases
Show Aluminium oxide reacting with a base and acid
- A₂O₃ (s) + 6H⁺ (aq) -> 2Al³⁺ (aq) + 3H₂O (l)
- A₂O₃ (s) + 2OH⁻ (aq) + 3H₂O (l) -> 2Al(OH)₄⁻ (aq)
Show the ionic equations and observations of Pb(II) with:
- Sodium hydroxide aqueous
- Excess sodium hydroxide aqueous
- Chloride ions
- Iodide ions
Additionally state what the only soluble salts of lead are.
- Pb²⁺(aq) + OH⁻ (aq) -> Pb(OH)₂ (s) white ppt
- Pb(OH)₂ (s) + 2OH⁻ (aq) -> [Pb(OH)₄]²⁻ colourless as the ppt redissolves
- Pb²⁺ (aq) + 2Cl⁻ (aq) -> PbCl₂ (s) white ppt
- Pb²⁺ (aq) + 2I⁻ (aq) -> PbI₂ (s) bright yellow ppt
- Must be lead (II) nitrate or lead (II) ethanoate
What is electron deficiency and what does this allow for aluminum chloride to do?
(3 marks)
- An atom that is electron deficient does not have a full outer shell. When group 3 elements form covalent compounds they only have 3 covalent bonds giving them only 6 electrons in their outer shell
- Aluminium and other group 3 elements form a co-ordinate bond to gain an electron pair
- Aluminium chloride forms a dimer with another aluminium chloride
Describe the bonding involved in BF₃NH₃ and the change of shape
(3 marks)
- Coordinate bonding
- NH₃ was pyramidal and BF₃ was trigonal
- Both are now tetrahedral
Describe Hexagonal Boron Nitride and make comparisons to graphie:
(6 marks)
- Both have layer structure
- Both isoelectric
- Both have lubricant properties due to weak VDW allowing layers to slide
- Graphite is an electrical conductor, but BN is an insulator
- BN layers are directly above each other, unlike graphite
- No delocalised electrons in BN, unlike graphite (insulator/conductor)
Describe the properties of cubic BN
(3 marks)
- Extremely hard and high melting point due to strong covalent bonds (giant covalent structure)
- Chemically inert
- Used for wear resistant coating
Describe the trend of stability in oxidation states going down Group 4
The +2 state increases in stability
