Key Points
Key Points: Group 18 Elements - The Noble gas Family
Electronic Configurations:
- General electronic configuration: ns² np⁶ (He = 1s²)
- Elements: He, Ne, Ar, Kr, Xe, Rn
- Noble gases have very high ionisation enthalpies and positive electron gain enthalpies — so they generally do not form compounds.
- First noble gas compound prepared by Neil Bartlett: \[\mathrm{O}_{2}(\mathrm{g})+\mathrm{PtF}_{6}(\mathrm{g})\longrightarrow\mathrm{O}_{2}^{+}[\mathrm{PtF}_{6}]^{-}(\mathrm{s})\] — since the ionisation enthalpy of Xe ≈ that of O₂, Xe was reacted similarly.
Shapes and Hybridisation of Xenon Compounds:
| Molecule | Hybridisation | Geometry | Shape |
|---|---|---|---|
| XeO₃ | sp³ | Tetrahedral | Pyramidal |
| XeO₄ | sp³ | Tetrahedral | Tetrahedral |
| XeOF₂ | sp³d | Trigonal bipyramidal | T-shaped |
| XeOF₄ | sp³d² | Octahedral | Square pyramidal |
| XeO₂F₂ | sp³d | Trigonal bipyramidal | Distorted trigonal bipyramidal (see-saw) |
| XeO₃F₂ | sp³d | Trigonal bipyramidal | Trigonal bipyramidal |
| XeO₃F₄ | sp³d² | Octahedral | Octahedral |
