Question

What is the correct Lewis structure for BF3?

1) 3 single bonds and 0 lone pairs
2) 2 single bonds and 1 double bond
3) 1 single bond and 2 double bonds
4) 0 single bonds and 3 double bonds

Answer 1

The correct Lewis structure for BF3 is 3 single bonds and 0 lone pairs around the central boron atom, with boron being electron-deficient and the molecule having a trigonal planar geometry with a net dipole moment of zero.

Step-by-step explanation:

The correct Lewis structure for BF3 (boron trifluoride) is option 1, which consists of 3 single bonds and 0 lone pairs around the central boron atom. Boron tends to form compounds where it does not achieve a complete octet, making BF3 an electron-deficient molecule. Furthermore, the molecular geometry of BF3 is trigonal planar. Each of the fluorine atoms has three lone pairs, and the boron center lacks a full octet, having only six valence electrons. Although it's possible to draw a structure that satisfies the octet rule with a double bond, experimental evidence suggests that the bond lengths are more consistent with single B-F bonds, indicating that the structure with single bonds is more representative of the actual molecule.

The trigonal planar structure results in all the B-F bond dipoles cancelling each other out, leading to a net dipole moment of zero for the molecule. Due to the identical B-F bonds, BF3 does not display any bond polarity despite being made up of atoms with different electronegativities.