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As shown on the Periodic Table, Carbon has a Ground State of
[He] 2s22p2 as represented by this orbital diagram.
6C
Ground State
2p2 2s2 [He]
[He] 2s2 2p2
[He]
Carbon
[He]
C2H2
NSF ATE DUE#1601612
A double bond (≡) is made of one sigma (σ) bond and two pi (π) bonds.
≡; 1σ + 2π
Triple Bonds: Ethyne
Notice there are only two singly occupied orbitals for bonding for each Carbon.
Promotion State
[He]
[He] 2s2 2p2
C2H2 bonds should all be equal, but remember that s bonds are stronger than p bonds, so nature has to do something to make the orbitals uniform.
That something is hybridization.
To create equal bond strength, we mix different orbitals and create one set of uniform hybrid orbitals for each Carbon.
As shown on the Periodic Table, Hydrogen has a Ground State of 1s1
1H
Hydrogen
sp3
p, 1
[He] 2s2 2p2
6C
p, 2
Hybridization State
p, 3
s
Hybrid Orbital
1
[He]
2
3
An electron is promoted to create four singly occupied orbitals for bonding for each Carbon.
To make C2H2, we need 4 singly occupied orbitals to bond for each Carbon.
4
H
Now that we have 2 uniform, singly occupied orbitals, we can bring in H to make Ethyne. The remaining hybrid orbitals overlap.
C
Linear
y axis
z axis
Tap/Click to Bond
x axis
1 σ bond
+
=
3 σ bonds total
2 π bonds total
explanation
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1 π bond
Explanation
3 total bonds