Final answer:
A cation is a positively charged ion formed when a neutral atom loses one or more electrons from its valence shell.
Step-by-step explanation:
A cation, which is a positively charged ion, is formed when a neutral atom loses one or more electrons from its valence shell. It is important to remember that cations have a positive charge. For example, a neutral sodium atom (Z = 11) has 11 electrons. If this atom loses one electron, it becomes a sodium cation (Na+) with a 1+ charge.