BF3 is a Lewis acid or Lewis base, explain?
The Correct Answer and Explanation is:
Correct Answer:
BF₃ (boron trifluoride) is a Lewis acid.
Explanation:
To determine whether BF₃ is a Lewis acid or a Lewis base, we need to understand the definitions involved. A Lewis acid is a substance that can accept a pair of electrons, while a Lewis base is a substance that can donate a pair of electrons.
BF₃ has a central boron atom bonded to three fluorine atoms. Each fluorine atom shares one pair of electrons with boron, forming three covalent bonds. However, boron in BF₃ has only six electrons in its valence shell, not the typical octet (eight electrons) seen in many stable molecules. This electron deficiency makes boron eager to accept an electron pair to achieve a more stable configuration.
Since BF₃ has an incomplete octet and can accept a pair of electrons from another molecule (such as from ammonia, NH₃, or water, H₂O), it functions as a Lewis acid. When BF₃ reacts with a Lewis base like NH₃, a coordinate covalent bond is formed between the nitrogen’s lone pair and the electron-deficient boron atom, completing boron’s octet.
On the other hand, BF₃ does not have any lone pairs on boron to donate to another atom, so it does not behave as a Lewis base.
Furthermore, despite the high electronegativity of fluorine atoms, the molecule does not donate electrons. Instead, the electronegative fluorine atoms pull electron density away from the boron atom, increasing boron’s tendency to accept electrons even more.
In conclusion, BF₃ is a Lewis acid because it is electron-deficient and has the ability to accept a lone pair of electrons from a donor molecule, thereby completing its octet.
