Answer
n = 1,2,3, .....
Work Step by Step
Possible values of n are:
n = 1,2,3,.....
Principle quantum number specifies the overall size and energy of an orbital. It is always an integer. A higher quantum number means a greater distance of an orbital from the nuclei and more energy. Hence, we can say that distance of an orbital from the nucleus and its energy is directly proportional to quantum number.