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My instructor has been drawing 3D molecules that show the directionality of non-bonding electron pairs and p-orbitals. I've been trying to find references online that show this process, but I'm having a hard time finding anything useful.

Can someone please explain the process or link to a source that does? I've included two pictures of molecules that show what I'm looking for.

enter image description here enter image description here

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  • $\begingroup$ Welcome to Chemistry.SX! I'll take the opportunity to point you to our tour which contains some useful information. Do I understand you correctly: You want to know why the p orbitals and free electron pair orbitals are drawn the way they are in your instructor's Lewis structure pictures? $\endgroup$
    – Philipp
    Sep 25, 2013 at 3:15
  • $\begingroup$ Thank you! I'm curious as to how these structures are drawn. For example, given some completely "random" molecule, how can I know how to draw the orbitals (and fill the electrons) the way they're presented here? $\endgroup$
    – Bob Dylan
    Sep 25, 2013 at 3:23
  • $\begingroup$ In order to give a helpful answer it might be good to know a little bit about your chemistry backgroud. Are you still in High School or at university (undergrad, grad student)? Do you know how to draw Lewis structures? Do you know what orbitals are (do you know basic quantum mechanics)? Do you know about conjugated bonds and such things? $\endgroup$
    – Philipp
    Sep 25, 2013 at 3:37
  • $\begingroup$ I'm an undegrad student. I know how to draw Lewis structures with nonbonding electrons, but I am specifically confused about the p orbits surrounding the carbon/oxygen atoms. Why does the bottom picture have two p orbitals (does this represent a triple bond?). $\endgroup$
    – Bob Dylan
    Sep 25, 2013 at 4:11
  • $\begingroup$ Regarding the lower picture, the right half does show a C-C-triple bond. What is their hybridisation? What does it imply on the geometrical arrangement between the atoms? Later, the horizontal dash between the carbon atoms, this symbolizes the sigma bond of rotational symmetry along the C-C direction. Black "lobes" perpendicular are for one set of pi-bonds, the curved line between them may remember you about their nickname, "banana bond". The blue lobes again perpendicular to these is the second set of pi-bond. On the left side, the hybridisation clearly differs. $\endgroup$
    – Buttonwood
    Feb 13, 2014 at 20:38

1 Answer 1

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As it is already pointed out in the comments, what you are learning for is hybridisation and some basic MO theory. Do not go too far into the MO direction, because you will get into somewhere completely different place, and you will hard time to make the connections.

So aftre you reviewed hybridization: Once you can identify in a molecule the sp1, sp2 and sp3 carbons, you should be able to orient the hybrid orbitals. For example in the case of sp2 carbon of the lower image, it is in the HHCC plane. In case of sp1 there are two, for sp2 one un-hybridized p orbitals. These unhybridized orbitals should be perpendicular to the hybridized ones: perpendicular to the axis of sp1 or the plane of sp2.

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