An atom is composed of protons, neutrons, and electrons. The number of protons in the nucleus determines the element's identity. The number of neutrons can vary, giving rise to different isotopes of an element. The number of electrons in an atom is equal to the number of protons, resulting in a neutral charge.

If an atom loses or gains electrons, it becomes an ion. Ions have a net electric charge and are either positively charged (cations) or negatively charged (anions).

In the given case, the number of protons is 7, and the number of electrons is 9. This means that the atom has gained two extra electrons, resulting in a net negative charge. Therefore, the atom is an anion.