Which of the following does form a Group II cation?

lead
iron
cobalt
nickel

How do you figure this one out?

You must know what is in group II. Fe, Co, and Ni are in group III. Pb is in both group I and group II. Pb ppts as the chloride in group I and as the sulfide in group II.

To figure out which of the given options form a Group II cation, you need to know the elements that belong to Group II on the periodic table.

Group II, also known as the alkaline earth metals, consists of elements such as beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

Among the options provided, lead (Pb) is the only element that belongs to Group II. It is worth mentioning that lead can also be found in both Group I and Group II.

To confirm this information, you can refer to the periodic table, scientific textbooks, or reliable online sources.