Can anyone explain to me why sulfur and phosphorus can sometimes have more than four electron pairs in atomic or covalent bonds?
It's about the topic of atomic bonding. I'm currently reading the textbook at that point.
Although phosphorus is in the 5th main group and would therefore need a maximum of 3 atomic bonds to fulfill the octet rule, and sulfur in the 6th main group needs 2 atomic bonds to fulfill the octet rule, both elements form more than the required number of bonds.
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I'm currently learning biochemistry from a biochemistry textbook for medical students. This book, "Human Biochemistry" by Florian Horn, is recommended for study at my university.
THE EXPLANATION in this book is as follows:
In short… There are more opportunities for bond formation because phosphorus and sulfur are less able to hold onto their outer electrons due to their large radius, as they are large atoms. Therefore, sometimes more than four electron pairs can be attached to the central atom. There's really no room for more than that.
I understand the thing about the large atoms and larger radius because they are in the third row of the periodic table and therefore have 3 shells, so the radius is larger.
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I understand it this way… Because of their larger radius, sulfur and phosphorus can lose outer electrons more easily because they aren't attracted as strongly to the nucleus, and this can result in four electron pairs instead of the usual three…
But that does not explain how there can be more than 4 electron pairs.
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Well, the explanation in the book is just completely undetailed, so I'm racking my brains now.
(No Ratings Yet)
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From the 3rd shell there are also d-orbitals. They were used earlier as an explanation for the so-called “Octett expansion”. A P atom having 5 bonds, for example in the PF5, would then be sp3d-hybridized with 6 bonds as in the PF6-sp3d2.
Such configurations are known from the transition metals, for example d2sp3, only here are 3p, 4s and 4p orbitals. “Newest” calculations, even 20 or 30 years old, have shown that the 3d-orbitals in the 3rd. Period energetically are too gloomy to play a role.
In fact – as far as we can talk about “actual” – s-sigma multi-centre bonds and sp-p-sigma three-centre bonds play a role, and then there are only 4.
You only understand the station? Then it doesn’t matter if you paint more than 4 bonds or exactly 4 with partial charges. They’re both incomplete models.
Okay, so I understand that in the dash formula you get elements from the 3rd. Period more electron pair bonds in the bar formula, because the 3d-orbital does not satisfy the third shell with 8 electrons. There’s a lot more to fit into the bowl.
The reason why in the 4th period (after the first two elements with 4s filling) only the d-orbital of the 3rd. Shawl is filled is an energetic reason, right? One can imagine that the 3d-orbital is closer to the core and therefore less attraction/energy/force is necessary to keep the electrons at the core/in the atom than the electrons of the 4th. Bowl (4p less well energetic, therefore 4p is not filled first) and therefore fills with elements of the 4. The 3d-orbital period? Is that right?
(And: The bar formula is only an aid and shows the real conditions only very rough. And geometric ratios can be approximately simulated with the lines?)
You seem to understand. Only there is not the d-orbital, but 5 of it. The totality of the d-orbitals is also called d-subshell. For p accordingly.
These are also more topics of physics chemistry. In biochemistry it comes to the configuration, trigonal-pyramidal, octahedral, etc., and to reactions. d-Orbitals are interesting in transition metal complexes, but how deep it goes into the subject, high- and low-spin e.g., I am overwhelmed.
Yes, interesting topic in itself. I’m just going over someone who doesn’t mind. Only I learn what a biochemistry exam and apparently there are some orbitals hidden, so I don’t learn that exactly. With all cycles like glycolysis, citrate cycle, etc., have enough learning material on the neck. I also have a part of physiological chemistry in biochemistry. May I have to learn the orbitals better for physiologist chemistry, then I will see. You have to limit some learning material.
The octet rule is a simple explanation model to not have to get in with the difficult stuff. It works with simple atoms, but not with all.
Depending on the state of knowledge, it is really easier if you simply accept that sulfur and phospor do not work only according to the octet rule.
As has been written, you need for a real understanding that Orbital model, which is the abrasive.
At this point you will probably be without Orbital model not really going on. So, if you have Bock, read more about it.