3.3 P-block Flashcards
What is meant by a P-block element?
- electronic configuration is where your last electron is in a p orbital
What happens as you descend group 4?
- become more ionic
- decrease in MP
Define the inert pair effect
- the resistance of S electrons to be involved in bonding due to a tendency of an S2 pair of electrons in an atom to stay paired, leading to a lower oxidation state
What happens to the inert pair effect as you descend groups?
- it gets stronger
Define electron deficiency
- where outer shells don’t have a full octet
Tin and carbon are stable in oxidation state +4 whilst lead is more stable as +2. Explain the difference instabilities of these oxidation states
- as you go down group 4 the inert pair effect becomes stronger
- the S electrons are more reluctant to be involved in bonding hence +2 is more stable than +4
How do electron deficient compounds fulfil their octet?
- form acceptor-donor compounds
- form dimers
What is meant by a dimer?
- when 2 of the same molecule join together using a coordinate bond
What is meant by an acceptor donor compound?
ie BF3 . NH3
- ammonia has lone pair to donate into boron to fulfil octet
- coordinately bonded
What enables octet expansion?
- empty d and f orbitals
Adding a lone pair reduces the bond angle by …?
2.5°
Explain why nitrogen can only form a chloride with 8 outer shell electrons, but phosphorus can form a chloride with a different number of outer shell electrons
- phosphorous can form a chloride with a different number of outer shell electrons as P3 elements have access to vacant d and f orbitals
- nitrogen cannot do this as it is P2 so does not have access to d and f orbitals
Reaction of sodium chloride with H2SO4
NaCl + H2SO4 —> NaHSO4 + HCl
- HCl has low oxidising power
- not redox
Reaction of sodium bromide with H2SO4
NaBr + H2SO4 —> HBr + NaHSO4
2HBr + H2SO4 —> Br2 + SO2 + 2H2O
- HBr has strong oxidising power
- redox reaction
Reaction of sodium iodide with H2SO4
NaI + H2SO4 —> HI + NaHSO4
2HI + H2SO4 —> I2 + SO2 + 2H2O
6HI + H2SO —> 3I2 + S + 4H2O
8HI + H2SO4 —> 4I2 + H2S + 4H2O
What happens to reducing power as you descend group 7?
- reducing power increases
Products and observations of NaF with H2SO4
HF - misty fumes
Products and observations of NaCl with H2SO4
HCl - misty fumes
Products and observations of NaBr with H2SO4
HBr - misty fumes
Br2 - brown fumes
SO2 - colourless gas with choking odour