what makes an ion

Atomic and Molecular Electrification

Species, whether atoms or molecules, exist with a neutral charge when the number of protons (positively charged subatomic particles in the nucleus) equals the number of electrons (negatively charged subatomic particles orbiting the nucleus). Perturbation of this balance results in a net electrical charge.

Cation Formation: Electron Depletion

A positively charged entity, a cation, arises from the removal of one or more electrons from a neutral atom or molecule. This loss of negatively charged particles leaves the species with a surplus of positive charge from the protons in the nucleus. The process of removing electrons requires energy, often referred to as ionization energy. The magnitude of the positive charge is directly correlated to the quantity of electrons detached.

Anion Formation: Electron Acquisition

Conversely, a negatively charged entity, an anion, originates from the addition of one or more electrons to a neutral atom or molecule. The acquisition of negatively charged particles yields an excess of negative charge relative to the positive charge of the protons. The addition of electrons typically releases energy. The magnitude of the negative charge is directly proportional to the quantity of electrons attached.

Polyatomic Examples

Electrification is not limited to single atoms; molecules can also gain or lose electrons to become polyatomic electrified species. For example, the hydroxide ion (OH-) is a common polyatomic anion, formed when the neutral hydroxide radical gains an electron. Similarly, the hydronium ion (H3O+) is a polyatomic cation formed when a water molecule accepts a proton (effectively losing an electron shared in a covalent bond).

Factors Influencing Formation

Several factors can influence the propensity for a species to become electrified. These include:

  • Electronegativity: Atoms with high electronegativity tend to attract electrons and form anions.
  • Ionization Energy: Elements with low ionization energies readily lose electrons and form cations.
  • Electron Affinity: A high electron affinity indicates a strong attraction for additional electrons, favoring anion formation.
  • Solvent Effects: In solution, solvation can stabilize electrified species, influencing their formation.
  • Applied Potential: Electrochemical reactions involving oxidation (electron loss) and reduction (electron gain) can be driven by an applied electrical potential.