Lewis Structure of Borane (BH3)
Borane (BH3) is a lewis acid and there are one boron atom and three hydrogen atoms in borane molecule. Each hydrogen atom has connected with boron through a single bond in the lewis structure of borane (BH3). There are only three bonds around boron atom and no lone pairs on boron atom. In this tutorial, we are going to learn how to draw the BH3 lewis structure.
BH3 lewis structure
According to the lewis structure of BH3, there are only six electrons around boron atom. Therefore, octal of boron atom is not completed. Therefore, borane molecule is a lewis acid.
Steps of drawing lewis structure of BH3
Following steps are the general guidelines to draw a lewis structure step by step. In this lesson, we use those rules to draw the BH3 lewis structure and they are explained in detail in next sections of this tutorial. If you are are beginner to lewis structure drawing, follow these sections slowly and properly to understand.
- Find total number of electrons of the valance shells of boron and hydrogen atoms
- Total electrons pairs
- Center atom selection
- Put lone pairs on atoms
- Check the stability and minimize charges on atoms by converting lone pairs to bonds until most stable structure is obtained.
Total number of electrons of the valance shells of BH3
- Boron is a group IIIA element. Therefore, boron has three electrons in its last shell.
- Hydrogen is a group IA element. Therefore, hydrogen has only one electron in its last shell.
- Total valence electrons given by boron atom = 3 * 1 = 3
There are three hydrogen atoms in BH3 molecule, Therefore
- Total valence electrons given by hydrogen atoms = 1 * 3 = 3
- Total valence electrons = 3 + 3 = 6
Total valence electrons pairs
Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells
Total electron pairs are determined by dividing the number total valence electrons by two. For, BH3, total pairs of electrons are 3 (= 6/2).
Center atom and sketch of BH3 molecule
There are some requirements to be the center atom. Having a high valence and being the most electropositive atom are leading requirements to be the center atom. In BH3, there are only two elements to select the center atom.
- Boron's maximum valence is 3. Hydrogen's maximum valence is 1. From that fact, boron has the high priority to be the center atom
- Boron's and hydrogen's electronegativity values are 2 and 2.1 respectively. Therefore boron is more electropositive than hydrogen. From that case too, boron has the highest chance to be the center atom.
- From above two facts, we can decide boron should be the center atom of BH3.
Mark lone pairs on atoms
- There are three B-H bonds in the above sketch. Therefore, there are no valence electrons pairs are remaining to draw the rest of the structure.
- So, there are no lone pairs to mark on boron and hydrogen atoms.
- The sketch we drawn above is the lewis structure of BH3.
Questions
BH3 total valence electrons
There are 6 valence electrons in BH3. Boron atom gives 3 valence electrons and each hydrogen atom gives 1 valence electron.
Are there charges on boron and hydrogen atoms in borane lewis structure
No. There are no charges on boron and hydrogen atoms in borane. But, boron atom has not fulfilled its octal.
does BH3 have resonance structures?
When lewis structure of BH3 is observed, we can clearly see, there are no resonance structures for BH3 because we cannot convert lone pairs to bonds or bonds to lone pairs with boron and hydrogen atoms.
What are the other lewis structures similar to BH3
When considering three sigma bonds and no lone pairs around borone atom, AlCl3 and AlH3 atre two examples
How many lone pairs on boron atom in BH3
There are no lone pairs on boron atom in BH3 lewis structure. Boron has only three electrons in its last shell and all of them contribute to make three single bonds with three hydrogen atoms. Therefore, there is no chance to exist lone pairs on boron atom.
How many lone pairs are on the boron atom in BH3 lewis structure?
There are 3 sigma bonds around boron atom and all three valence electrons of boron atom are contributed for those sigma bonds. Therefore, there are no lone pairs on boron atom in BH3.