Yes, all monatomic cations have a positive charge. A cation is an ion that has lost one or more electrons, resulting in a net positive charge. In the case of monatomic cations, which are formed from single atoms, the positive charge arises when an atom loses one or more electrons from its outermost energy level. This loss of electrons creates an imbalance between the number of protons (positive charges) and electrons (negative charges) in the atom, resulting in a net positive charge.
For example, sodium (Na) is a monatomic cation that forms when a sodium atom loses one electron. The loss of the negatively charged electron leaves behind a positively charged sodium ion (Na+). Similarly, other monatomic cations such as calcium (Ca2+), iron (Fe3+), and hydrogen (H+) also have positive charges due to the loss of electrons.