Final answer:
The single cation of rubidium (Rb), which is Rb+, would have 36 electrons since it loses one electron compared to its neutral state that contains 37 electrons.
Step-by-step explanation:
The single cation of rubidium (Rb) would have 36 electrons. Rubidium in its neutral state has 37 electrons, but when it forms a cation, it loses one electron.
This loss of an electron results in a positively charged ion known as a cation. The abbreviated electron configuration for rubidium (Rb) before it loses an electron is [Kr]5s¹.
Once it becomes a cation (Rb+), the electron configuration reflects the loss of that single electron, resulting in [Kr]. Therefore, a Rb+ ion has one less electron compared to neutral rubidium.