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What is the geometry of the fluorine atoms around the boron atom in BF4^–?  (A) ...

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lak-86 | Student, Undergraduate | Salutatorian

Posted August 20, 2013 at 3:57 AM via web

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What is the geometry of the fluorine atoms around the
boron atom in BF4^–? 
(A)  planar 

(B)  see-saw
(C)  tetrahedral 

(D)triangular pyramidal

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llltkl | College Teacher | Valedictorian

Posted August 20, 2013 at 8:01 AM (Answer #1)

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The geometry of the fluorine atoms around the central atom (boron) in `BF_4^-` can be evaluated from the VSEPR model.

From the Lewis structure of `BF_4^-` ,

Number of valence electrons of the central atom (B): 3

Electrons shared+electrons obtained from dative contribution during bond formation: 3+2=5

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Total: 8 electrons = 4 pairs

pi bonded pairs (if any): 0

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Number of structurally active electron pairs around the central atom: = 4-0 = 4

Hybridization: `sp^3` ,

Geometry: Tetrahedral,

Lone pairs (if any): 0

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Hence the fluorine atoms are disposed around boron atom in exact tetrahedral arrangement (option C).

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