An ion (ˈaɪ.ɒn,_-ən) is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons while an anion is a negatively charged ion with more electrons than protons. Opposite electric charges are pulled towards one another by electrostatic force, so cations and anions attract each other and readily form ionic compounds. Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron and a positive ion. Ions are also created by chemical interactions, such as the dissolution of a salt in liquids, or by other means, such as passing a direct current through a conducting solution, dissolving an anode via ionization. The word ion was coined from Greek neuter present participle of ienai (ἰέναι), meaning "to go". A cation is something that moves down (κάτω pronounced kato, meaning "down") and an anion is something that moves up (ano ἄνω, meaning "up"). They are so called because ions move toward the electrode of opposite charge. This term was introduced (after a suggestion by the English polymath William Whewell) by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday did not know the nature of these species, but he knew that since metals dissolved into and entered a solution at one electrode and new metal came forth from a solution at the other electrode; that some kind of substance has moved through the solution in a current.

About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Related courses (26)
CH-432: Structure and reactivity
To develop a detailed knowledge of the key steps of advanced modern organic synthesis going beyond classical chemistry of olefins and carbonyls.
MICRO-624: Wearables and implantables for personalized and preventive healthcare
This multidisciplinary course presents, from both engineering and medical perspectives, the state-of-the-art, applications and impact of wearable and implantable technologies, with focus on cardiovasc
MSE-600: Effects of radiation on materials
The purpose of this course is to provide the necessary background to understand the effects of irradiation on pure metals and on alloys used in the nuclear industry. The relation between the radiation
Show more
Related MOOCs (8)
Plasma Physics and Applications [retired]
The first MOOC to teach the basics of plasma physics and its main applications: fusion energy, astrophysical and space plasmas, societal and industrial applications
Plasma Physics and Applications
The first MOOC to teach the basics of plasma physics and its main applications: fusion energy, astrophysical and space plasmas, societal and industrial applications
Plasma Physics: Introduction
Learn the basics of plasma, one of the fundamental states of matter, and the different types of models used to describe it, including fluid and kinetic.
Show more

Graph Chatbot

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.