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I saw a proper debate going on between answers to a question about whether the octet rule could be violated. Some people were pointing to hypervalency in period 3 elements, due to the available d-orbitals that are empty. Apparently, this interpretation has been pretty much disproven by real-life measurements of bond energy not corresponding with the bond energy that would exist in a hypothetical hypervalent molecule. But with the neat and simple explanation of hypervalency excluded, how does one explain molecules like SF6, or SO4? I suspect half-bonds are involved, but I don't even understand how a half bond can exist. One cannot split an electron in half (in this context at least), so how can a half bond exist?

Please explain to me as if I'm a High School student that's really learning more about the factory side of chemistry and is therefore not so acquainted with the more theoretical side of chemistry. Don't get me wrong, I love the theoretical side of chemistry, and anything mildly advanced within chemistry that I know is self-taught, but because of this, I have a lot of holes in knowledge and terminology. So, be painstakingly clear if you could :)

A. Kvåle
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    https://chemistry.stackexchange.com/questions/19433/how-can-iodine-bond-with-5-fluorines-in-iodine-pentafluoride https://chemistry.stackexchange.com/questions/105649/the-real-structure-of-difluorodioxoxenon-xeo2f2 – Mithoron Sep 07 '20 at 18:29
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    https://chemistry.stackexchange.com/questions/4760/why-do-compounds-like-sf6-and-sf4-exist-but-sh6-and-sh4-dont – Mithoron Sep 07 '20 at 21:09
  • It was talked about far too many times and tends to attract answers that do not take into consideration like anything that was found out during last half a century. – Mithoron Sep 07 '20 at 21:12
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    Does this answer your question? Hypervalency and the octet rule – Sir Arthur7 Sep 08 '20 at 04:07
  • @SirArthur7 Not really, I didn't understand the explanations. And it wasn't conclusive either. Maybe there still isn't a conclusion, but that question was asked 5 years ago. Surely there has been some change in confidence in either the octet rule always being adherered to, or hypervalency being the answer. – A. Kvåle Sep 08 '20 at 15:37
  • See this answer https://chemistry.stackexchange.com/a/5242/9961 and this one https://chemistry.stackexchange.com/a/134402/9961 – Mithoron Sep 09 '20 at 23:42

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Hypervalency is real, yes. Hypervalency is the ability of an atom in a molecule to expand its valence shell beyond the limits of the Lewis octet rule. Hypervalent compounds are common for the second and subsequent row elements in groups 14–18 of the periodic table.

Half bonds don't exist. The closest thing to a half bond is e.g Li2+, H2+. Its a one-electron bond. One-electron bonds often have about half the bond energy of a 2-electron bond, and are therefore called "half bonds".

Ollie
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