Total Number of Vibrational Stretching Modes for CO2 Molecule

CO2 molecule has three atoms. The carbon atom is bonded to two oxygen atoms through double bonds. The CO2 molecule has a linear shape, which means that the atoms are in a straight line. The total number of vibrational stretching modes for CO2 molecule is three.

Types of Vibrational Stretching Modes

The vibrational stretching modes for CO2 molecule are of two types:

1. Symmetric Stretching Mode: In this mode, both the oxygen atoms move towards the carbon atom and away from it simultaneously. The carbon atom remains stationary. This mode has a frequency of 2349 cm-1.

2. Asymmetric Stretching Mode: In this mode, one oxygen atom moves towards the carbon atom while the other moves away from it. The carbon atom remains stationary. This mode has a frequency of 667 cm-1.

Why are there Only Three Vibrational Stretching Modes?

The CO2 molecule has three atoms and two double bonds. The two double bonds present in the molecule have a higher bond order than a single bond. As a result, they have a greater stiffness and higher force constant. This means that they vibrate at a higher frequency compared to a single bond. Since there are only two double bonds in the molecule, there can only be two possible stretching modes. The third mode is the bending mode.

Conclusion

In conclusion, the CO2 molecule has three vibrational stretching modes, out of which two are symmetric and asymmetric stretching modes, and the third is the bending mode. The symmetric stretching mode has a frequency of 2349 cm-1, and the asymmetric stretching mode has a frequency of 667 cm-1.