When an atom or molecule gains electrons, it is said to be what?

When an atom or molecule gains electrons, it is called reduced. This process is fundamental to redox reactions, where reduction occurs simultaneously with oxidation. In these reactions, oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.

The term "reduced" reflects the decrease in the oxidation state of the atom or molecule as it acquires negatively charged electrons. This shift alters the overall charge balance and can significantly impact the chemical properties and reactivity of the species involved. Understanding reduction is crucial in various biological processes, including cellular respiration and photosynthesis, where electron transfer is a key component.

In contrast, ionization typically refers to the process of an atom or molecule gaining or losing one or more electrons, resulting in a charged species, but it does not specifically indicate the electron gain associated with reduction. Neutralization, on the other hand, involves the reaction between acids and bases, leading to the formation of water and salts, and is not directly related to the gain of electrons. Thus, the concept of reduction is specifically tied to the gain of electrons, making it the correct term in this context.