When we look at the periodic table, we can observe the placement of many elements to find out the charge of its ion. Family, or group, one elements form +1 ions while group two elements from +2 ions. This is because groups one and two need one and two electrons to complete their outermost electron orbit respectively. Group 18 elements, the noble gases, do not form ions. Group 17 elements, the halogens, form -1 ions, and group 16 elements form -2 ions because they need to give away one and two electrons to have a full outermost electron orbit respectively. Though we can see that transition metals form positive ions, and some transition metals have set charges, most transition metals are extremely variable, and depending on what element they bond with, they can become one of many different ions. Why does this happen? Because it is a lot easier for transition metals to lose electrons compared to the alkaline earth metals (groups one and two). This is because transition metals have 5 d-orbitals. D-orbitals have a variety of oxidation states, whereas the s-orbitals in the alkaline earth metals cause these metals to have set oxidation states. For example, in CoBr2, we see that Cobalt is +2 because Bromine is a +1 ion, and two Bromines create a charge of +2. In the molecule CoN, Cobalt has a +3 charge because Nitrogen forms a -3 charge, and to make the molecule neutral, Co has to be +3.
