Question

Most of our discussion of transition metals has focused around them becoming positively charged ions. However, many of the transition metals will also become negatively charged ions. Using what you have learned from quantum mechanics and about electron configurations, predict which transition metals are most likely to form anions with a charge of -1 and explain the prediction.

Answer 1

As we know, element that donats elecrons are metals. so metals are are positive in first look. But if you consider a complex, then the oxidation state of that metal may vary and it can be negative also. like Mn . Quantum aspects are mentioned below-

The oxidation state of a transition metal in a crystal lattice is conventionally viewed as reflecting physical ionization: electrons have been transferred to or from the atom, leaving a point-like charged entity (ion). Such a picture is still sometimes invoked to describe the properties of, for example, transition-metal oxides. Yet quantum mechanical calculations suggest that, regardless of formal oxidation state, the local charge on the transition metal atoms is largely unchanged. Scientists rationalize this behaviour by looking at the response of the hybrid bonds, formed between the atom and its host crystal, to the addition or removal of electrons. They identify a self-regulating process that shifts the energy levels of these bonds in such a way that the local charge on the transition metal atom remains approximately constant.