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The p-Block Elements — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryThe p-Block Elements2 Marks
Question
Explain why $\mathrm{BCl}_3$ is monomer but $\mathrm{BH}_3$ exists as $\mathrm{B}_2 \mathrm{H}_6$.
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Answer

In $\mathrm{BCl}_3$, there is back bonding, i.e., lone pair of electrons is donated from chlorine to boron thus reducing its electron deficiency.
In $\mathrm{BH}_3$, back bonding is not possible but H -bridges are possible, therefore, it exists as dimer.

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