When an electron of a one-electron atom is excited to the second shell, it will occupy the 2s orbital rather than the 2p orbital. In one-electron systems, such as hydrogen-like atoms, the energy levels only depend on the principal quantum number (n), which represents the shell or energy level of the electron.
The energy levels in an atom can be represented as follows:
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < ...
The "s" orbitals have a lower energy than the "p" orbitals within the same shell. Therefore, when an electron is excited to the second shell, it will initially occupy the 2s orbital before filling the higher-energy 2p orbitals.