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Abhisar
 one year ago
Can anyone teach me how to write configuration for heteroatomic molecules using MOT. Eg. \(\sf H_2O\)
Abhisar
 one year ago
Can anyone teach me how to write configuration for heteroatomic molecules using MOT. Eg. \(\sf H_2O\)

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Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1I am doing it like \(\sigma 1s^2 ~\sigma^*1s^2~\sigma 2s^2~\sigma ^*2s^2 (\pi 2p_x^1 \pi2p_y^1)\)

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1But according to this there are 2 unpaired electrons and thus water should be paramagnetic but water is actually diamagnetic.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Your problem is here in the \(\sigma ^*2s\) orbital's placement. It's actually higher in energy than the \(\pi\) orbitals. \(\sigma 1s^2 ~\sigma^*1s^2~\sigma 2s^2~\sigma ^*2s^2 (\pi 2p_x^1 \pi2p_y^1)\) So the correct placement should be: \(\sigma 1s^2 ~\sigma^*1s^2~\sigma 2p_z^2(\pi 2p_x^2 \pi2p_y^2)~\sigma ^*2p_z^0 \) Which has only paired electrons, thus diamagnetic like you're looking for. Also note that I changed them from s to \(p_z\). Remember these \(\sigma\) molecular orbitals came from two p orbitals not s orbitals! Here's the difference in a picture! dw:1439133799765:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I think my picture got cut off so here I found one on the internet: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/graphics/fig8_32.gif http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/graphics/fig8_30.gif See how both combine to give \(\sigma\) orbitals bonding and antibonding?

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1ok, will you write the configuration similarly for \(\sf B_2\) ?

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1I am sure that for homonuclear molecules like \(\sf N_2, B_2\) energies for molecular orbitals are in order \(\sigma 1s <\sigma^*1s<\sigma 2s<\sigma ^*2s <(\pi 2p_x\approx~\pi2p_y)\)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0\(B_2\) is different than what you might expect depending on what you know. It obeys what's called "light bonding scheme" where the two orbitals are flipped relative to other homonuclear diatomic molecules found in the same period as \(B_2\) And here's a pic of the MO diagram in case you were curious: http://img.sparknotes.com/figures/8/83ce1fb7be648ede5785ea60c96b495c/b2correlate.gif Writing it out should follow from this, I started typing it and got lost in all the pi's and sigmas and subscripts so I'll just let you figure that out and I can check you, but you can see where all the electrons are placed. Also, since the lower orbitals don't contribute to bonding, usually people omit them in case you were looking for the 1s orbitals.

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1Yes that's what I am confused, the scheme followed by heteronuclear molecules like HF and H2O seems to be different. I want to learn how to write their configuration.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0You are correct, to add to what you've written: \(\sigma 1s <\sigma^*1s<\sigma 2s<\sigma ^*2s <(\pi 2p_x\approx~\pi2p_y) < \sigma2p_z <(\pi 2p_x^*\approx~\pi2p_y^*) < \sigma2p_z^* \)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Well I think this is a good picture showing the differences: http://chemwiki.ucdavis.edu/ @api/deki/files/10245/MO_diff_Diagram.jpg?size=bestfit&width=384&height=288&revision=1 I got it from here: http://chemwiki.ucdavis.edu/Theoretical_Chemistry/Chemical_Bonding/Pictorial_Molecular_Orbital_Theory/How_to_Build_Molecular_Orbitals I sort of hesitate to give any solid answers here because you have to realize that these are just models and not entirely true, so I have forgotten some of the specific details, but how to combine heteronuclear diatomics and how they mix rely on the electronegativity differences, electrons will tend towards for instance oxygen, which is because that's a lower potential energy state as opposed to hydrogen. Don't read the next part lol In reality you sorta have to determine these with more sophisticated mathematics using wavefunctions and/or actual experiments... or other hand wavy sounding reasoning. For instance water's real MO diagram will look like this http://www.brynmawr.edu/chemistry/Chem/sburgmay/chem231/MOpics/H2Omos.jpg

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1Thanks for the help, I really appreciate it :)

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1I actually kinda get it now, this video is a good explanation https://www.youtube.com/watch?v=estiedAlXII

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Cool yeah I have to review this topic I'm trying to get into graduate school but I'm sorta practicing inorganic and physical chemistry right now, but I really love organic chemistry so if you have any more fun questions I really need to practice and look stuff up haha

Abhisar
 one year ago
Best ResponseYou've already chosen the best response.1Sure, I'll keep it coming as I encounter them. Thanks for the help again :)
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