- 1). Define what makes an element positively or negatively charged. The outer layer of an atom of an element wants to have as many electrons in it as possible. When an atom ionizes, it will take whatever step is easier for it to have a full outer layer--one without too many electrons or too few. If it's easier to gain electrons, the atom will gain them, thereby becoming negatively charged. If it's easier to lose them, the atom will become positively charged.
- 2). Identify positive elements. As a rule, most elements in columns one, two, three and 14 from the left have ions with positive charges. These columns are called Groups. The elements in these Groups are structured in a way that they lose electrons when they ionize, leaving them with more protons than electrons and a positive overall charge. Most of the transition metals, which range from Group 3 through Group 12, have positive charges as well.
- 3). Identify negative elements. On the other side, Groups 15, 16 and 17 on the periodic table gain electrons when they ionize. Therefore, atoms of these elements will have negative charges because they end up with more electrons than protons.
- 4). Review the exceptions. As with most things in science, there are exceptions to all of these
rules. The periodic table is arranged to give you a good idea of ionic charges, but some elements never form ions naturally so they don't have a charge. Carbon is an example of this type of element. Use quality scientific sources to find charges for ions of specific elements.
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