What Is an Atom That Gains or Loses an Electron Called?
An atom that gains or loses an electron is called an ion. This change in electron count gives the atom a net electrical charge. If it loses an electron, the atom has more protons than electrons and becomes a positively charged cation. If it gains an electron, the atom has more electrons than protons and becomes a negatively charged anion.
How Ions Form and a Quick Example
The process of gaining or losing electrons happens during chemical reactions, often when atoms bond with each other. Metals tend to lose electrons easily, while nonmetals tend to gain them. For example, a sodium atom (Na) has 11 protons and 11 electrons, making it neutral. It has a single electron in its outer shell that it can lose. When sodium loses that electron, it becomes a sodium ion (Na⁺) with 11 protons and only 10 electrons. The net charge is +1. This is a cation. On the other side, a chlorine atom (Cl) has 17 protons and 17 electrons. It needs one more electron to fill its outer shell. When chlorine gains an electron, it becomes a chloride ion (Cl⁻) with 17 protons and 18 electrons, giving it a net charge of -1. This is an anion. The naming conventions for these charged species are defined by organizations such as the IUPAC and are fundamental to understanding chemical bonding and compound formation, as explained by the Royal Society of Chemistry.
The charge on an ion is usually written as a superscript after the element symbol. A single positive or negative charge uses a plus or minus sign (Na⁺, Cl⁻). Larger charges use a number followed by the sign, such as Mg²⁺ (magnesium ion with a +2 charge) or O²⁻ (oxide ion with a -2 charge). Ion formation is driven by atoms achieving more stable electron configurations, often filling or emptying their outer electron shell.
Key Takeaways
- An atom that gains or loses an electron is called an ion.
- Losing an electron produces a positively charged cation; gaining an electron produces a negatively charged anion.
- The charge on an ion is written as a superscript (e.g., Na⁺, Cl⁻, Mg²⁺).
- Ion formation is driven by atoms achieving more stable electron configurations.
