1. The Basics

* Oxygen Atom: A neutral oxygen atom has 8 protons (positively charged) and 8 electrons (negatively charged). This makes it electrically neutral.

* Oxide Ion: An oxide ion (O²⁻) has gained two extra electrons. It now has 8 protons and 10 electrons, giving it a net charge of -2.

2. The Process

Oxygen atoms are highly electronegative, meaning they have a strong attraction for electrons. This means they tend to gain electrons to achieve a stable electron configuration.

* Gaining Electrons: Oxygen atoms typically gain two electrons to achieve a full outer shell of 8 electrons. This stable configuration is like that of the noble gas neon.

* Becoming an Ion: When an oxygen atom gains two electrons, it becomes negatively charged and is now called an oxide ion (O²⁻).

3. Examples

Oxide ions are common in many compounds:

* Oxides: Metal oxides like magnesium oxide (MgO) are formed by the reaction of a metal with oxygen. The oxygen atoms gain electrons from the metal atoms, forming oxide ions.

* Hydroxides: Hydroxide ions (OH⁻) contain an oxide ion bonded to a hydrogen atom. They are found in bases like sodium hydroxide (NaOH).

In summary, an oxygen atom becomes an oxide ion by gaining two electrons to achieve a stable electron configuration, resulting in a net negative charge of -2.