We propose an orbital-selective model for the transport and magnetic properties of an individual Co impurity deposited on the Pt(111) surface. Using a combination of an Anderson-type Hamiltonian and Kubo's linear response theory we show that the magnetization and dI/dV spectrum of the Co adatom originate from the 3d states of different symmetry. A textbook expression for the spin-dependent differential conductance provides a natural connection between magnetic and transport properties of Co/Pt(111). We found that it is possible to detect and to manipulate the different 3d states of the Co adatom by tuning the tip-impurity distance in scanning tunneling microscopy experiments.