EasyChemistryHigh School (11–12)The p-Block Elements › Groups 17 and 18: Halogens and Noble GasesNumericalConceptualA-LevelIB
Find the number of lone pairs on xenon in 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.
Find the number of lone pairs on xenon in XeF2, XeF4 and XeF6. Then find the steric number of xenon trioxide, XeO3, where each Xe=O counts as one region and uses 2 electrons of xenon. Name the shape of each of the four species.
Need a reminder? The key ideaShow
Xenon has 8 outer electrons, and each fluorine atom uses one of them. A double bond to oxygen counts as one region and uses 2 electrons. XeF2, XeF4 and XeF6 are made from Xe and F2 in the ratios 1 : 1, 1 : 2 and 1 : 3. The hydrolysis of XeF6 gives XeO3 and HF. In a disproportionation the same element is oxidised and reduced.
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. XeF2. . Steric number 5. The lone pairs are in the middle plane. Linear.
Step 2. XeF4. . Steric number 6. Square planar.
Step 3. XeF6. . Steric number 7. Distorted octahedral.
Step 4. XeO3. The three oxygen atoms use electrons. lone pair. Steric number . Trigonal pyramidal.
Answer: 3, 2 and 1 lone pairs, a steric number of 4 for XeO3, and the shapes above.
Check. XeO3 has the same shape as the chlorate ion, which also has 3 bonded oxygen atoms and one lone pair.
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