You will find that molecules with triple bonds are similar to molecules with
double bonds in the way that unhybridized
p orbitals on the central atoms overlap sideways with each other.
In order to understand molecules with triple bonds, you need to understand
molecules with linear molecular structure.
How many unhybridized p orbitals were there
on the central atom for the linear molecular structure?
In the following 3D applet, there are two central white atoms that are bonded to each other.
A separate red atom is bonded to each of the central white atoms.
Molecules with triple bonds are described in Chapter 10 in your textbook.
Place the cursor over the molecule, press and hold the left button down, and move the mouse.
You should be able to spin the molecule in any direction, and examine the orientation of
the atoms. (If the image looks weird, like it is only partially shown or it looks like a double image,
click the refresh button of your browser. It is at the top in the toolbar.)
Convince yourself that all of the atoms, whether they are white or red, all lie in the
same geometric line.
Convince yourself, also, of the similarity of the triple bond molecular structure with the
linear molecular structure.
The following 3D applet shows the same molecule with the unhybridized p orbitals on the central white atoms.
This 3D applet is a bit busy, so rotate it carefully to fully appreciate the orientation
of the atoms and the unhybridized p orbitals on the central atoms.
Acetylene, CHCH, is the simplest molecule with a triple bond between the central atoms. Recall
in the linear molecular structure, beryllium was the central atom, and it did
not obey the octet rule.
In contrast, the carbon atoms in acetylene obey the octet rule.
How many electrons from each central carbon atom would occupy the unhybridized p orbitals?
Hint, think Lewis formulas.
Note that unhybridized p orbitals are drawn in such a way that they are touching one other.
(Rotate the molecule slowly to convince yourself that they are touching.) The unhybridized p orbitals are
said to overlap each other. The electrons that occupy the unhybridized p orbitals on each central atom
are shared between the overlapping p orbitals.
Note that there are two separate sets of overlapping p orbitals on the central white atoms.
How would you describe the geometric orientation of the two sets
of overlapping p orbitals?
How would you describe the geometric orientation of each
of the sets of overlapping p orbitals with the geometric line of atoms?
There is a sigma bond between the two central white atoms shown as a blue line in the 3D applet.
What is the hybrid of the orbitals on the central atom that make the sigma bond?
Hint, what hybridized orbitals were the two bonds in the
linear molecular structure?
How many sigma and pi bonds comprise a triple bond?
URL: http://www.rretc.com/chemistry/triple_bonds.html
Copyright (c) 2006 with Michael Keyes (michael.keyes@rretc.com)
Feel free to use for single-user, educational purposes only. All other purposes, please email.