What is an ion?
An ion is a charged atom or molecule. It is charged because the number of electrons do not equal the number of protons in the atom or molecule. An atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.
When an atom is attracted to another atom because it has an unequal number of electrons and protons, the atom is called an ION. If the atom has more electrons than protons, it is a negative ion, or ANION. If it has more protons than electrons,it is a positive ion.
History and Meaning
The term "ion" was introduced by English chemist and physicist Michael Faraday in 1834 to describe the chemical species that travels from one electrode to another in aqueous solution. The word ion comes from the Greek word ion or ienai, which means "to go."
Although Faraday could not identify the particles moving between electrodes, he knew that metals dissolved into a solution at one electrode and that another metal was deposited from the solution at the other electrode, so matter had to be moving under the influence of an electrical current.
Examples of ions are:
alpha particle He2+ hydroxide OH-