How many electrons are in a rubidium ion (rb+)?

The atomic number of a Rubidium atom is 37. If the substance is neutral which means that the charge is zero, the substance would have 37 electrons. Knowing that the charge is positive for Rubidium ion, this means that one electron has been lost. The answer is therefore, 36. 

Step-by-step explanation:

2x6²( = 2x36 ) =  72