What is the Lewis dot structure of BF3
The correct answer and explanation is:
Correct Answer: Lewis Dot Structure of BF₃
The Lewis dot structure of boron trifluoride (BF₃) is:
F
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F - B - F
Each fluorine (F) atom has three lone pairs of electrons, and each forms a single bond (a shared pair) with the central boron (B) atom. The boron atom is surrounded by three bonds and no lone pairs, totaling six valence electrons—which is less than an octet.
Detailed Explanation (Approx. 300 words)
The Lewis dot structure is a simple way to represent the valence electrons of atoms in a molecule and how those electrons are arranged in bonds.
Step 1: Count valence electrons
- Boron (B) has 3 valence electrons.
- Each fluorine (F) has 7 valence electrons.
- BF₃ has 1 boron + 3 fluorine atoms = 3 + (3×7) = 24 valence electrons total.
Step 2: Identify the central atom
- Boron (B) is the least electronegative (excluding hydrogen) and is placed at the center.
Step 3: Form single bonds
- Connect each fluorine to the boron using a single bond.
- Each bond uses 2 electrons × 3 bonds = 6 electrons used.
Step 4: Distribute remaining electrons
- We have 24 – 6 = 18 electrons left.
- Distribute these electrons to the fluorine atoms to satisfy their octets.
- Each F gets 6 more electrons (3 lone pairs) × 3 = 18 electrons used.
Step 5: Check the octets
- Each fluorine has 8 electrons (3 lone pairs + 1 bond).
- Boron has only 6 electrons (3 single bonds), which is less than an octet.
But this is acceptable because boron is an exception to the octet rule—it is stable with only six electrons.
Step 6: Check formal charges
- All atoms have a formal charge of zero, making this structure stable.
Conclusion
BF₃ is an example of a molecule where the central atom (boron) does not follow the octet rule. It forms three covalent bonds with fluorine atoms, and each fluorine completes its octet with lone pairs. This structure accurately represents the molecule’s bonding and stability.