The atomic number of an element X is 13. What will be the number of electrons in its ion $X^{3+}$?

The correct option is D

10

If the atomic number of an element X is 13; the number of electrons in its ion $X^{3+}$ will be 10. This is because $X^{3+}$ is a positively charged cation. An atom loses electrons from its valence shell and becomes positively charged ion called cation. Here, Atom X loses 3 electrons and acquires 3+ charge. Therefore the number of electrons lost will be 3 and the number of electrons in its ion $X^{3+}$ will be 10.