Which option correctly defines ionization?

• A. Ionization is when a neutron is absorbed by the nucleus
• B. Ionization is when an electron is removed from the atom
• C. Ionization is the emission of a gamma ray
• D. Ionization is when an atom gains an electron

Answer: (B)

Ionization is the process of removing one or more electrons from an atom, creating positively charged ions and free electrons. This requires energy that overcomes the atom’s binding energy (ionization energy). In radiation protection, ionizing radiation is defined by its ability to cause such electron removals in matter, leading to charged particles that can cause biological damage.

The option describing removal of an electron best captures this concept. Neutron absorption is a nuclear event, not ionization. Emission of a gamma ray is a form of energy release from a nucleus or atom, not the act of removing an electron. Gaining an electron corresponds to reduction, producing a negatively charged ion rather than an ionized atom with a missing electron.