Which ion is formed when sodium loses an electron?

When sodium loses an electron, it transitions from a neutral atom to a positively charged ion. Sodium, represented as Na, has an atomic number of 11, meaning it has 11 protons and 11 electrons in its neutral state. By losing one electron, the total number of electrons decreases to 10, while the number of protons remains unchanged at 11. This imbalance results in a net positive charge.

The ion formed in this process is Na⁺, which indicates that it has a single positive charge due to the loss of one electron. This is a common occurrence for alkali metals like sodium, as they tend to easily lose one electron to achieve a stable electronic configuration, similar to that of noble gases.

The other choices represent ions that do not occur in this context. Na⁰ would indicate a neutral sodium atom with no charge, while Na²⁺ and Na³⁺ suggest the loss of two and three electrons, respectively, which is not typical for sodium under normal circumstances. Such multiple positive charges would require significant energy and different conditions than simply losing one electron. Thus, the correct representation of the ion formed when sodium loses an electron is Na⁺.