Question

the infrared spectrum above represents the absorption of certain wavelengths of radiation by molecules of co₂. which of the following best explains what occurs at the molecular level as the co₂ molecules absorb photons of the infrared radiation?
a the atoms in the co₂ molecules increase their vibration as the bonds between the atoms bend and stretch.
b the molecules of co₂ increase the energy of their rotational motions.
c the electrons in the valence shells of the atoms in the co₂ molecules are promoted to higher electronic energy levels.
d the bonds between the atoms in the co₂ molecules are continuously broken and then re - form.

Explanation:

Infrared radiation causes molecular vibrations. When $CO_2$ molecules absorb infrared - radiation photons, the atoms in the $CO_2$ molecules vibrate more as the bonds between the atoms bend and stretch. Rotational motions are associated with microwave radiation, electron promotion with ultraviolet - visible radiation, and bond - breaking is not a typical result of infrared absorption under normal conditions.

Answer:

A. The atoms in the $CO_2$ molecules increase their vibration as the bonds between the atoms bend and stretch.