Question

Absorption of ultraviolet light by organic molecules always results in what process?

A. Bond breaking
B. Excitation of bound electrons
C. Vibration of atoms in polar bonds
D. Ejection of bound electrons

Answer 1

Absorption of UV light by organic molecules primarily results in the excitation of bound electrons, where an electron jumps to a higher energy state.

Step-by-step explanation:

Absorption of ultraviolet (UV) light by organic molecules always results in the excitation of bound electrons. When a molecule absorbs energy from UV light, an electron within the molecule is excited from a lower energy molecular orbital to a higher energy orbital. This process can lead to various outcomes, including fluorescence, bond breaking, or ionization, depending on the energy of the UV light and the strength of the molecular bonds.

High-energy UV light has the potential to ionize atoms or break up tightly bound molecules owing to the significant photon energy, approximately 10 eV, which is enough to disassociate many weakly bound molecules. Nonetheless, the immediate effect of UV light absorption is the excitation of electrons.

While UV light can break bonds and cause damage at the cellular level, especially when protective ozone is depleted, it primarily causes electronic excitation in organic molecules. Therefore, the answer to the question is B: Excitation of bound electrons.