Final answer:
Cobalt in its ground state has three unpaired electrons. The number of unpaired electrons in cobalt complexes can vary; for example, [CoF6]3- has four unpaired electrons.
Step-by-step explanation:
The element cobalt (Co) in its lowest energy state, which is also known as the ground state, has an electronic configuration of [Ar] 3d7 4s2. To determine the number of unpaired electrons, we consider the 3d electrons. Cobalt, which has seven electrons in the 3d subshell, will have three of these orbitals contain paired electrons and two orbitals containing a single electron each. Therefore, cobalt will have a total of three unpaired electrons in its ground state.
As for cobalt complexes, the number of unpaired electrons can vary depending on the ligands and the overall charge of the complex. For example, the high spin complex [CoF6]3-, influenced by weak field ligands, can indeed have up to four unpaired electrons. However, it is important to note that having six unpaired electrons would require a transition metal with a d6 configuration in a high spin state, which is not the case for cobalt.