What does ionization refer to?

Ionization refers specifically to the process by which an atom or molecule gains or loses electrons, resulting in the formation of charged particles known as ions. When a neutral atom loses one or more electrons, it becomes positively charged, while gaining electrons results in a negatively charged ion. This process is fundamental in various contexts, such as in chemistry, physics, and even in skin care, where certain treatments utilize ionizing methods to enhance the penetration of products into the skin.

Transforming into a gas pertains to a physical change in state rather than a change in electrical charge. The mixing of different particles does not inherently involve changes to their electronic structure or charge state, and disintegration of substances generally refers to breaking down into smaller components, not specifically into ions. Therefore, the correct answer that accurately describes ionization is the separation into positive or negative ions.