singlet oxygen

Singlet oxygen is not a chemical element. It refers to an electronically excited state of molecular oxygen (O₂). In its ground state, oxygen has two unpaired electrons with parallel spins, which is known as a triplet state. When oxygen absorbs energy, such as from light, it can transition to a singlet state, where the electrons have opposing spins. This singlet state is highly reactive and can cause damage to biological molecules.1

Oxygen (O) is a chemical element, atomic number 8, essential for life. It is a colorless, odorless gas that makes up about 21% of Earth's atmosphere. Oxygen readily forms compounds with most other elements, playing a crucial role in combustion and respiration.2