This equation applies only to the hydrogen atom, for which Z =1. The product of the constants is given by
(1) What energy is required to move an electron from n=1 to n=2 in a hydrogen atom?
The additional energy needed to excite an electron to the second shell from the first is
The sign of the energy change is important. Because the sign is positive, energy must be added to move an electron from the first shell to the second shell. The necessity of adding energy agrees with the fact that the second energy shell is a higher energy shell than the first energy shell.
