An ion with more electrons than protons is known as an anion.
Ions consist of atoms or groups of atoms with a negative or positive charge. If they have gained electrons, they will be negatively charged, as they have more electrons than protons, and are called anions. These ions are usually composed of more than one atom, making them polyatomic ions, and are usually built around a central atom, typically a non-metallic one.
Chlorine and other halides form negatively charged anions.
Common anions include acetate, hydroxide, carbonate, chlorate, cyanide, fluoride, nitrate, phosphate and oxide. Except for hydroxide and cyanide, all ending in -ide are monatomic. Group 7 atoms called halides, which include elements such as fluorine, chlorine, bromine, and iodine, form negatively charged anions. Elements such as oxygen and sulfur carry a negative charge of two, while nitrogen and phosphorus carry a negative charge of three.
Chemists can determine more about anions through experimentation and calculation.
Most polyatomic ions combine with oxygen and/or hydrogen to form an anion. In these ions, the negative charge, or electron, is shared around the entire ion, not within a specific nucleus of the ion. They are also known as negative ions, while positive ions are called cations. Cations are atoms that have lost an electron and, as a result, have a positive charge. Both are often found in water because of the nature of the molecule.
Negative and positive ions are found in water.
The physical properties of an anion differ from those of a cation. It polarizes the electron clouds of molecules in the opposite way to that of cations. Furthermore, these ions have weakly bound electron densities, which leads to a high probability of polarization or resistance of an electrolytic cell. They have stronger interactions with nearby molecules than neutrals and cations, which are less likely to polarize.
The binding energy of electrons in an anion is less than in a neutral or cation. A negative ion does not normally experience an excited electronic state. Furthermore, its electrons will move to regions of space occupied by orbitals to experience an attractive potential different from that experienced by neutrals and cations.
Anions tend to bind outer electrons more tightly than neutrals and cations, which makes it difficult to create a lot of them. Electronically or geometrically stable, or those that do not separate or fragment, generally bind excess electrons in their orbitals. This allows for easy analysis and chemists can determine more about them through experiments or calculations.