Why are single bonds weaker than double?
1 Answer
Simply from how they're constructed. Since a pure double bond consists of 1
All pure single bonds consist of one
Below is an example a constructive
2p_z-2p_z head-on overlap that forms asigma_(2p_z) molecular orbital, where electron density lies in the white bulged region---between the atoms.
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A nice example is the
\mathbf(sigma) bond in\mathbf("Cl"-"Cl") .
All pure double bonds consist of an additional
Below is an example of the
2p_x-2p_x constructive/bonding overlap, where electron density lies in the white bulged region (above the atoms).
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An explicit
pi bond example is the\mathbf(pi) bond in\mathbf("O"="O") , a product of either a2p_x-2p_x sidelong overlap, or a2p_y-2p_y sidelong overlap (but not both), that forms api_(2p_(x"/"y)) orbital, depending on which pair overlaps.This
pi bond is made in addition to thesigma bond that was already made upon forming the first"O"-"O" bond.
Therefore, since a pure double bond consists of 1