By Carolyn LaRoche, Updated Mar 24, 2022
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Atoms can acquire an electrical charge by either losing or gaining electrons, becoming ions. A positively charged ion is called a cation, while a negatively charged ion is known as an anion. Ions play a central role in ionic bonding, which creates many of the compounds we encounter daily.
Every atom contains protons (positive), neutrons (neutral), and electrons (negative). Electrons orbit the nucleus and can move between atoms. When an atom loses one or more electrons, it becomes a cation. Conversely, when an atom gains electrons, it becomes an anion. The balance between protons and electrons determines the ion’s charge.
Metals, which dominate the periodic table, readily lose electrons to achieve a stable electron configuration. The resulting cations typically carry a positive charge that corresponds to the number of electrons lost. The charge varies by the metal’s group:
Because free electrons are abundant in metals, they conduct electricity efficiently, a property directly linked to cation formation.
Nonmetals, located on the right side of the periodic table, tend to gain electrons to fill their valence shells. These additional electrons create a surplus of negative charge, forming anions. The typical charges depend on the nonmetal’s group:
Unlike metals, nonmetals do not conduct electricity because electrons are tightly bound to their atoms.
Understanding ion formation helps explain a wide range of chemical phenomena—from how salt dissolves in water to how biological cells maintain electrical gradients. Recognizing the pattern of charges across the periodic table also aids in predicting the behavior of elements in chemical reactions.
