MediumChemistryHigh School (11–12)Chemical Bonding › Shapes of Molecules and HybridisationConceptualNEETBoard ExamAPA-LevelIB
Xenon is a noble gas with 8 outer electrons, yet it forms XeF₂, XeF₄ and XeF₆…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Xenon is a noble gas with outer electrons, yet it forms , and . Find the electron pairs and lone pairs on xenon in each, and predict the shapes of and .
Need a reminder? The key ideaShow
VSEPR theory: count the electron pairs on the central atom as . Here is its outer electrons, its singly bonded atoms and the charge, added for an anion. Pairs spread out: 2 linear, 3 trigonal planar, 4 tetrahedral, 5 trigonal bipyramidal, 6 octahedral. Lone pairs repel more than bonding pairs. The shape names only the positions of the atoms. With five pairs, lone pairs take equatorial positions.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. . pairs, two bonding, lone pairs. All three lone pairs take the equatorial triangle. The two fluorines are left on the axis, so the molecule is linear.
Step 2. . pairs, four bonding, lone pairs. The lone pairs sit opposite each other, so the four fluorines make a square planar molecule.
Step 3. . pairs, six bonding and lone pair. Seven pairs do not fit a simple shape, and the molecule is a distorted octahedron.
Answer: has 3 lone pairs and is linear; has 2 lone pairs and is square planar.
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