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Ecap

Hello!

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I stumbled upon this forum. This is great! Over the last year or so I have really taken an interest in chemistry...

There are a couple concepts I am a bit confused about. Despite having scored good grades in my classes, I have to admit that my knowledge is pretty limited to "bookish" chemistry - in other words - completing problem sets!!

I am curious about orbital hybridization. I know the orbitals based on the periodic table, and can predict the hybridization of an atom within a molecule based on the lewis dot structure.

However, I'm not sure how or why hybridization occurs. In class it was described as the "promoting" of an electron to a free orbital within a valence shell, usually a p orbital. What does this mean, exactly? Do the repulsions of simultaneously-orbiting electrons force other electrons into different "orbital shapes" (ie., s, p, d, f ) to minimize electromagnetic interference? Is this 'electron promotion' really as regular as classroom hybridization would have me believe?

Also, what happens when you start forming compounds with elements in the "d" block? I notice strange things with manganese. KMno4-1, MNO2, all these variations occur (unlike Na, which produces highly predictable +1 ions). Anyways, just bantering...

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welcome:) always nice to see someone with a genuine interest in chemistry. there's a few of us here.

 

It sounds to me like you've learned about hybridisation and so on but not the crucial quantum mechanics behind it. Most textbooks have a chapter on basic quantum mechanics... it usually starts with the nature of waves, then proceeds to wave-particle duality, the photoelectric effect, then the Bohr atom and finally quantum mechanics. I figure you'd probably enjoy reading that chapter, especially if it's not covered in your chemistry course. I teach chemistry to two classes, the general class and the advanced class... the course for the general one doesnt include that chapter and it makes it SO much more difficult to teach the chapters afterwards, particularly the stuff involving hybridisation.

 

I'm not sure about the description of hybridisation you give. It's not really about the promotion of an electron, but more about changing of the actual orbitals the electrons are "in". (electrons are often said to be "in" an orbital but electrons ARE the orbitals). The common example is when an "s" orbital is combined with three "p" orbitals to form four sp3 orbitals. The four new orbitals are all exactly the same energy as each other, where the s orbital was lower in energy than the p orbitals, so if there was an electron in the s orbital it was promoted to the sp3 orbital. However, if there were any electrons in any of the p orbitals, they were demoted to sp3.

 

your question about manganese is a good one. However it's hard to answer quickly... manganese can form more oxidation states than most other elements, and ranges from totally ionic bonds to totally covalent bonds. It even forms [ce]Mn2O7[/ce] which is crazy stuff... why it does that is not so easy to explain.

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