A Free Radical is an atom (or a molecule) with an "unpaired electron" in the outer ring.
An unpaired electron also means that this particle has an odd number of electrons since the "pairing" of electrons always goes by twos.
Do you remember your grade nine science? Protons have a positive electrical charge. Electrons have a negative electrical charge. The electrons move around the central mass made up of protons and neutrons. Neutrons have no electrical charge.
Let's take for example, the element helium. The helium atom has two electrons circling around its core, which consists of two protons and two neutrons. If one of those electrons "goes away", the second electron no longer has a mate - that's a free radical! Suddenly this particle has an odd number of electrons (it only has one) in the outer ring (the only ring). We should note however that it's very difficult to take one electron away from a helium atom, and that's why helium is considered to be extremely stable - a noble gas.
Oxygen is not so stable, and that's why its a common ingredient in reactions that create free radicals. Once an oxygen atom has fewer electrons (with a negative electrical charge) than it does protons (with a positive electrical charge) then the atom itself is negatively charged and becomes a free radical that scours its environment looking for electrons to steal.
Let me re-iterate these basic concepts. A "free radical" is an atom with an unpaired electron in the outer ring. It's lacking an electron. Does a free radical always have to be just one atom? No. It can also be a molecule, made up of two or more atoms.
Here are some molecules that are free radicals. This is actually the Free Radical hit parade: These charged particles are the most common bad guys! They are called Reactive Oxygen Species or ROS for short. Notice they all contain oxygen:
- Hydroxyl radical HO
- Alkoxyl radical RO
- Peroxyl radical ROO
- Hydrogen peroxide H2O2
- Superoxide anion radical O2-
- Singlet oxygen 1O2
- Nitric oxide radical NO
- Peroxynitrite ONOO
Many scientists now believe that free radicals are responsible for 99% of all human disease. Why? Because these nasty little charged particles steal electrons from molecules in healthy cells and thereby cause inflammation - which causes disease.
