Question
Nuclear reactions transform one nuclide into another. Fission, splitting a large nucleus into two smaller nuclei, releases vast amounts of energy.
(i) Uranium hexafluoride, $\mathrm{UF}_6$, is used in the uranium enrichment process that produces fuel for nuclear reactors.
State the molecular shape of uranium hexafluoride.
(ii) Explain why uranium dioxide, $\mathrm{UO}_2$, has a very high melting point whereas uranium hexafluoride vapourises easily into gas.
▶️Answer/Explanation
Markscheme
i
octahedral
Accept “square bipyramidal”
ii
$\mathrm{UO}_2$ strong bonding throughout crystal structure
$\mathrm{UF}_6$ molecular «covalent bonds between atoms» $A N D$ London/dispersion/instantaneous induced dipole-induced dipole forces between molecules
Accept “UO $\mathrm{O}_2$ has ionic lattice”