Final answer:
Valences with the greatest tendency to form ions include +1, +2, +3, -1, -2, and -3, corresponding to the main group elements on the periodic table like alkali metals, alkaline earth metals, and halogens.
Step-by-step explanation:
The valences that have the greatest tendency to form ions are typically +1, +2, +3, -1, -2, and -3. These charges correspond to the main group elements on the periodic table which readily lose or gain electrons to achieve a noble gas electron configuration. For instance, group 1 elements (alkali metals) tend to form +1 ions, group 2 elements (alkaline earth metals) form +2 ions, and group 17 elements (halogens) form -1 ions. It's also common for group 16 elements to form -2 ions, and for group 15 elements to form -3 ions. These tendencies are because the elements in these groups have 1, 2, and 3 valence electrons or are 1, 2, or 3 electrons short of a full octet, respectively. Transition metals, such as those that can form +2 or +3 ions like iron and copper, have variable oxidation states and their tendencies to form certain ions can be less predictable.