BH3 Lewis structure

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BH3 Lewis Structure
BH3 Lewis structure

BH3 (borane) has one boron atom and three hydrogen atoms.

In the BH3 Lewis structure, there are three single bonds around the boron atom, with three hydrogen atoms attached to it, and none of the atoms has a lone pair.


Use these steps to correctly draw the BH3 Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required

Let’s discuss each step in more detail.

#1 First draw a rough sketch

  • First, determine the total number of valence electrons
Periodic table

In the periodic table, boron lies in group 13, and hydrogen lies in group 1.

Hence, boron has three valence electrons and hydrogen has one valence electron.

Since BH3 has one boron atom and three hydrogen atoms, so…

Valence electrons of one boron atom = 3 × 1 = 3
Valence electrons of three hydrogen atoms = 1 × 3 = 3

And the total valence electrons = 3 + 3 = 6

  • Second, find the total electron pairs

We have a total of 6 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 6 ÷ 2 = 3

  • Third, determine the central atom

Here hydrogen can not be the central atom. Because the central atom is bonded with at least two other atoms, and hydrogen has only one electron in its last shell, so it can not make more than one bond.

Hence, here we have to assume that the central atom is boron.

Therefore, place boron in the center and hydrogens on either side.

  • And finally, draw the rough sketch
BH3 Lewis Structure (Step 1)
Rough sketch drawn, and got the stable Lewis structure of BH3

#2 Mark lone pairs on the atoms

Here, we have a total of 3 electron pairs. And three B — H bonds are already marked. So we do not have to mark any electron pair as a lone pair on the sketch.

In the above structure, you can see that the central atom (boron) doesn’t form an octet. But, boron has an exception that it does not require eight electrons to form an octet. So no need to worry about the octet rule here.

Therefore, this structure is the stable Lewis structure of BH3.

Next: C2H6 Lewis structure

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