Final answer:
When an oxygen atom loses an electron, it becomes a positively charged cation with a net charge equal to the number of electrons lost.
Step-by-step explanation:
An oxygen atom has 8 protons. When it loses an electron, it becomes a positively charged cation because the number of protons remains the same while the number of electrons decreases. For example, if an oxygen atom loses 2 electrons, it will have 8 protons and 6 electrons, resulting in a net charge of +2.
Learn more about Properties of atoms