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Bit confused on how these two differ regarding their position on the internuclear axis. Believe Dr. Lavelle said Sigma bonds occur on the axis while Pi bonds are around the axis. What does this really mean about the electron interaction between two atoms? For Pi bonds one electron is above the other?
Sigma bonds occur on the internuclear axis, meaning the axis created by the interaction between the nucleus of two bonded atoms. Pi bonds occur when the orbitals are next to each other, allowing for the electrons to pair up, and this is not necessarily done on the internuclear axis. Pi bonds make it so that there is essentially two areas that attach the atoms to each other rather than one, and this prevents the atom from rotating independent of the molecule.
Sigma bonds interact end to end and allow bound atoms to rotate. They have cylindrical symmetry around the internuclear axis. Pi bonds overlap side by side and do not allow bound atoms to rotate without breaking bonds. Pi bonds result in electron density above and below the internuclear axis.
Hi! Sigma bonds involve two orbitals which interact end to end with each other; whereas a pi bond also involves two orbitals but instead of interacting end to end, they overlap side to side. Thus, the orbitals in a pi bond cannot be rotated or else the pi bond will break; however, sigma bonds allow bound atoms to rotate. Hope this helps! :)
Sigma bonds allow bound atoms to rotate, thus the resulting sigma bond has electron density with cylindrical symmetry around the internuclear axis. On the other hand, pi bonds are between 2 orbitals, each with one electron, which are overlapped side by side, and thus the 2 regions of electron density are above and below, not along the internuclear axis.
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