sigma and pi  [ENDORSED]

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Julie Barreto 3A
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sigma and pi

Postby Julie Barreto 3A » Thu Oct 20, 2016 7:08 pm

How do you calculate the valence electron configuration using sigma and pi

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Re: sigma and pi  [ENDORSED]

Postby Chem_Mod » Mon Oct 24, 2016 12:32 pm

I am not sure I understand your question exactly. It would be helpful to refer to a question or page in the textbook or course reader. I will try to answer as completely as possible.

When we refer to valence electrons of an atom, we are referring to the maximum of 8 electrons that can occupy the outermost s and p subshells. To determine the number of valence electrons in an atom or ion, simply write out its electron configuration. The two highest energy (highest principle quantum number) s and p subshells contain the valence electrons.

When writing Lewis structures, we use Valence-bond (VB) theory and the valence electrons of the atoms involved to form bonds and lone pairs. All bonds are made of two shared valence electrons. A single bond is made up of a single sigma bond. A double bond is a sigma and pi bond. A triple bond is a sigma and two pi bonds. Thus, a sigma bond is made up of two valence electrons while a pi bond is made up of 4 valence electrons.

I believe you are referring to molecular orbital (MO) theory diagrams. In such diagrams, molecular orbitals are constructed by combining the individual atomic orbitals in a bonding pair. The s orbitals combine to form a bonding and antibonding sigma orbital while the p orbitals are combined to form one bonding and antibonding sigma orbital and two bonding and antibonding pi orbitals. Writing their electron configuration is just a matter of listing these MOs and their electron occupancies (in superscript) from lowest to highest energy.

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