I honestly have no clue where to begin explaining why the Si-F bond is one of the strongest single covalent bonds of them all.

I would actually predict the bond to be relatively weak on account of the relatively large size of the Si atom leading to a relatively long bond length and hence poor orbital overlap. Indeed, Si's valence orbitals being large and diffuse further suggest to me that the overlap with F's small concentrated orbitals is poor.

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    $\begingroup$ I think you need a source to support that Si–F is indeed the strongest single covalent bond; I was under the impression that B–F was the strongest (although that number is probably unduly influenced by backbonding in BF3 & similar compounds). And wiredchemist.com/chemistry/data/bond_energies_lengths.html agrees with me. $\endgroup$ Dec 22, 2019 at 21:29
  • $\begingroup$ @orthocresol I'm afraid that I have no better source than my lecturer. After looking at this website wiredchemist.com/chemistry/data/bond_energies_lengths.html, it would appear that the B-F bond is indeed stronger than the Si-F bond. I'm still curious to know why the Si-F bond is so strong. $\endgroup$
    – ETS
    Dec 22, 2019 at 21:34
  • $\begingroup$ Before you ask "why", ask "if". $\endgroup$ Dec 22, 2019 at 21:36
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    $\begingroup$ A long bond does not necessarily mean that it is weaker. A strong overlap between orbitals will also increase the same-spin (Pauli) repulsion, so more overlap does also not necessarily mean stronger bond. It is usually a delicate balance between many factors. $\endgroup$ Dec 22, 2019 at 22:03


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