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How can the formation of $\ce{BF_4^-}$(Boron is $\ce{sp^3}$ hybridized) be explained using VBT and Hybridization? So far, I understood that one electron from s orbital gets excited and jumps into a p orbital, and then the orbitals undergo $\ce{sp^3}$ hybridization leaving us with four $\ce{sp^3}$ hybrid orbitals (three $\ce{sp^3}$ orbitals with one electron each and one $\ce{sp^3}$ hybridized orbital with no electron). What happens next?

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Perhaps my answer deals mostly with hybridisation and less with VBT. Your question seems to be arising when you find that only 3 of them contain a lone electron each and the fourth is still empty despite the hybridisation being $\ce{sp^3}$ which means total four hybrid orbitals.

Well, see that you asked about fluoroborate ($\ce{BF_4^-}$) in which there is an excess charge on boron. What happens first is, as you pointed out, that an electron from s orbital jumps to a p orbital. There is still one empty p orbital which acquires an electron and thus a negative charge on B. Now what you have is four singly occupied $\ce{sp^3}$ orbitals of B that can each overlap with a lone electron in the p orbital of four F atoms to give $\ce{BF_4^-}$.

Note that the hybridisation to $\ce{sp^3}$ doesn't happen unless the remaining p orbital of boron gets at least one electron.

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    $\begingroup$ I didn't add this image to my answer as it is out of context of your question but could still be useful. $\endgroup$ Commented May 25, 2023 at 11:10
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    $\begingroup$ That was really well explained. Thank you. $\endgroup$ Commented May 25, 2023 at 12:33
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    $\begingroup$ No, please, no. This produces a completely incorrect image of what is happening. This only furthers the most common misconception. Hybridisation is only a mathematical description, it's not a cause and there certainly are no electrons jumping around. I have to down vote this. $\endgroup$ Commented May 25, 2023 at 15:09
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    $\begingroup$ It is important to understand that there are electron clouds and nuclei. They arrange in some sort of geometry. This is the basis. The elections don't know where they came from and they don't know where they are going. Hybridisation is a mathematical description of one way of forming a wavefunction. That is the basis of Valence bond theory. There is simply not enough space in the comments or in an answer to explain that. It needs a textbook and probably a good one at that $\endgroup$ Commented May 25, 2023 at 20:05
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    $\begingroup$ Just for good measure: Valence Bond Theory cannot explain the formation of a molecule (or ion). It can only describe the bonding within under the constraint that this geometry exists. $\endgroup$ Commented May 25, 2023 at 20:08

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