If a certain atom gains electrons its oxidation number will be:

Explanation

If a certain atom gains electrons, its oxidation number will decrease. In other words, the oxidation number of the atom becomes more negative. Remember that oxidation number (also known as oxidation state) is a way to represent the distribution of electrons in a compound or ion. When an atom gains electrons, it becomes more negatively charged and therefore has a lower oxidation number. This is because electrons have a negative charge, so when an atom gains electrons, it becomes more negatively charged and its oxidation number decreases. For example, consider the reaction: Cl₂ + 2e⁻ → 2Cl⁻ In this reaction, chlorine (Cl) gains two electrons to become chloride ions (Cl⁻). The oxidation number of chlorine decreases from 0 in Cl₂ to -1 in Cl⁻. This reduction of oxidation number indicates the gain of electrons.