Cation vs Anion- Definition, 10 Major Differences, Examples

Cation Definition

A cation is an atom or a group of atoms bearing one or more positive electric charges.

• Cations are formed in various ways, some of which are:
  • When electrons are removed from neutral atoms or ions or other molecules.
  • By the combination of positive ions with other molecules.

• By rupture of covalent when causes the shared paired of electrons is associated with one atom, and the other one becomes deficit.
• Cations are usually formed from metal atoms; however, positive radical ion might also have multiple atoms like in ammonium ion (NH₄⁺).
• Cations are positively charged because they have more protons than electrons. Thus, cations are electron deficit.
• The size of cations is measured by measuring their ionic radius and cations, in general, have a smaller radius as they usually have one orbit less than their corresponding parent atoms.
• Hydrogen is the smallest cation that has no electron and thus is much smaller than its parent atom.
• In crystalline solids, the anions occupy most of the space in the lattice and cations are thus present between those spaces.
• Cations in the gaseous state are highly reactive and will react with anions to form neutral molecules. However, cations might be present in both liquid or solid-state.
• In the liquid state, cation interacts with the solvent to form solvated ions which are much stable.
• Because these are charged particles, their movements can be deflected by magnetic fields.
• Under an electric field, cations move towards the negative terminal (anode) to form neutral atoms. Most metals are purified by this process where they are platted onto the anode plate in an electric field.
• Cations are given different names to indicate the number of charges carried by these particles. Dications are cations with two positive charges, and trications are cations with three positive charges.
• Similarly, positively charged ions formed from organic molecules are termed carbocations.

Anion Definition

An anion is an atom or a group of atoms bearing one or more negative electric charges.

• Anions are formed in various ways, some of which are:
  • When electrons are added to neutral atoms or ions or other molecules.
  • By the combination of negative ions with other molecules.

• By rupture of covalent when causes the shared paired of electrons to be associated with one atom resulting in a negative charge.
• Anions are usually formed from non-metals; however, negative radical ions might also have multiple atoms like in sulfate ion (SO₄^—).
• Anions are negatively charged because they have more electrons than neutrons. Thus, anions are electron-rich.
• The size of ions is measured by measuring their ionic radius and anions, in general, have a larger radius as they usually have more electrons that repel each other creating a larger size than their corresponding parent atoms.
• Anions occupy most of the space in the crystal of solids as they have a larger size.
• Anions in the gaseous state are highly reactive and will react with cations to form neutral molecules. However, anions might be present in both liquid or solid-state.
• In the liquid state, anion interacts with the solvent to form solvated ions which are much stable.
• Under an electric field, anions move towards the positive terminal (cathode) to form neutral atoms.
• Most non-metallic gases are obtained by this process where they are collected from the positive terminal (cathode) of an electric field.
• Anions are given different names to indicate the number of charges carried by these particles. Dianions are anions with two negative charges, and trianions are anions with three negative charges.
• Similarly, negative ions formed from organic molecules are termed carbanions.

Key Differences (Cation vs Anion)

Example of Cation

Sodium-ion

• Sodium atom is a monoatomic monocation that is formed from the ionization of sodium atom.
• Sodium is a metal that during the breaking of bonds, gives the shared pair of electrons to the anion, thus carrying a positive charge.
• The molecular formula of sodium ion is Na⁺ with an ionic radius of 0.102 nm.
• Sodium ions are necessary for several physiological activities in the body like regulation of body fluids like blood, the transmission of nerve impulses, heart activity, and other metabolic functions.
• Sodium is important in other animals, as it is maintained at a high concentration in their blood and other extracellular fluids, but the ion is not necessary for plants.
• Humans require less than 500 mg per day of sodium in their diet.
• However, in people with salt-sensitive blood pressure, extra intake of sodium may cause a negative effect on health.

Example of Anion

Chloride ion

• Chloride ion is a diatomic monoanionic that is formed from the ionization of the chlorine atom.
• Chlorine is a non-metal that during the rupturing of bonds, takes the shared pair of electrons, resulting in a negative charge.
• The molecular formula of the chlorine ion is Cl^– with an ionic radius of 0.181 nm.
• Chloride ion is an essential electrolyte present in almost all body fluids. It is responsible for transmitting nerve impulses, maintaining acid/base balance, and regulating fluid in and out of cells.
• The kidneys carefully control the number of chloride ions in the blood.
• Chloride-transporting proteins (CLC) are a particular type of protein that plays fundamental roles in many tissues, in the cell membrane as well as in intracellular membranes.
• CLC proteins form a gene family that comprises nine members in mammals, at least four of which are involved in human genetic diseases.

References and Sources

• National Center for Biotechnology Information. PubChem Database. Sodium-ion, CID=923, https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-ion (accessed on July 13, 2020)
• National Center for Biotechnology Information. PubChem Database. Chloride ion, CID=312, https://pubchem.ncbi.nlm.nih.gov/compound/Chloride-ion (accessed on July 13, 2020)
• 3% – https://www.ncbi.nlm.nih.gov/pubmed/17729441
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