Electronic configuration of Rb = 1s2, 2s2, 2p6, 3s2, 3s24s23d10,4p6 5s1.
The outer electronic configuration is ns1, for the 5th period n = 5 hence Principal quantum number, n = 5
Azimuthual quantum number, l = 0 (s orbital l = 0)
Magnetic quantum number m = 0 (l = 0, there is only one m value i.e. 0)
Spin quantum number, s = +1/2 or – 1/2 (there is only one electron and it can have clockwise or anticlockwise spins).
The four quantum number of Rb is 5, 0, 0, +1/2.
