Research studies on students' conceptions in the area of quantum physics are, in contrast to other areas of physics, rather rare. The present study gives results from quantitative and qualitative data with grade 13 students (age 19) in German high schools, taken before and after instruction as well as from transcripts during instruction. Only students from classes, which used a Schroedinger approach to understand atoms and electron orbitals, were taken. As a first result, we describe students' beliefs about models. Students tend to use "model" in a variety of meanings, ranging from "true pictures" to "tools of thinking" and "visualization". Second, we describe their conceptions about orbits, trajectories, and motion, mainly related to their interpretations of orbitals, after teaching. The findings suggest, that roughly 25% of the students use conceptions near to modern physics, another 25% use some typical intermediate conceptions such as "smeared orbits", and 50% stick to classical orbits ("Bohr model"), even after teaching. Third, we give results about their understanding of "stability" of the atom, "probability", and "energy". The problem of stability brings nearly all students back to classical thinking in terms of orbit and centrifugal force. Probability, again, has different meanings related to the algorithm or to a causal explanation of a probability distribution or to inaccuracy. The quantization of energy is readily accepted, even without a conception related to orbitals of the atom.