What is the Lewis dot structure of #BH_3#? How many lone pair electrons are in this molecule? How many bonding pairs of electrons are in this molecule? How many lone pair electrons are at the central atom?

1 Answer
anor277
May 23, 2016

Well, there are 6 electrons to distribute in #BH_3#, however, #BH_3# does not follow the pattern of #"2-centre, 2 electron"# bonds.

Explanation:

Boron has 3 valence electrons, and hydrogen has the 1; thus there are 4 valence electrons. The actual structure of borane is as diborane #B_2H_6#, i.e. #{H_2B}_2(mu_2-H)_2#, in which there are #"3-centre, 2 electron"# bonds, bridging hydrogens which bind to 2 boron centres. I would suggest that you get your text, and read in detail how such a bonding scheme operates.

By contrast, in ethane, #C_2H_6#, there are enough electrons to form #7xx"2-centre, 2 electron"# bonds, i.e. the #C-C# linkage, and #6xx"C-H"# bonds.

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