Abstract Nuclei in the 1d-2s shell are grouped according to their last odd nucleon number. Their properties are examined strictly within the framework of the extreme single particle Nillsson model. The effect of band mixing is included in a consistent way. Properties, such as energy spectra, magnetic moments and E2 and M1 transitions of odd-mass nuclei with Z or N = 9, 11 and 13, can be well described by the model. However, when Z or N = 15, it is not possible to fit these properties with a consistent variation of the parameters of the Nilsson potential Nuclei with Z or N = 17 exhibit low-lying core excitations and therefore the extreme single particle model is not valid for them.