Lewis Electron- Dot Structure of boron fluoride BF molecule - #41

A simple and general method for writing Dot Structures - Lewis Structures is given in a previous article entitled “Lewis Structures and the Octet Rule”. Relevant worked examples were given in the following articles: Examples #1, #2, #3 , #4, #5, #6,  #7,  #8, #9, #10, #11, #12, #13, #14,  #15, #16, #17, #18, #19, #20, #21, #22,  #23,  #24, #25, #26, #27, #28, #29, #30, #31, #32, #33, #34 , #35, #36 ,  #37,  #38,  #39 and #40. 

Let us consider the case of the BF molecule. Boron monofluoride is an unstable gas but forms stable ligands when combines with transition metals¹, like the CO molecule. The experimental BF bond length has been found to be 1.263 Angstrom. The bond order for the BF bond has been calculated to be 1.4.²

Step 1: Connect the atoms with single bonds. 

Fig. 1 : Connect the atoms of the BF molecule with single bonds.

 Step 2:  Calculate the # of electrons in π bonds (multiple bonds) using  Lewis structure formula (1): 

Where n in this case is 2 since BF consists of two atoms.

Where V = (3 + 7) = 10 , V is the number of valence electrons of the ion.

Therefore, P = 6n + 2 – V = 6 * 2 + 2 – 10  = 4     So, there are 2 double or 1 triple bond.

Since there are only 2 atoms in the BF molecule there is no possibility that 2 double bonds will be present.    

Step 3 & 4: The  Lewis electron dot resonance structures of  BF   are as follows:

Fig. 2 : Plausible Lewis Resonance Structures of boron fluoride

 

Resonance structure #3 is the most plausible since there is no charge separation. Lewis resonance structure #2 is more possible than #1 since there is less charge separation.

Quantum mechanical and theoretical studies have shown that the bond order in BF is ~1.4 – the bond between the B and the F atom is between a single and a double bond.