What Is an Ion?
An ion is simply an atom or molecule that is electrically charged.
Ionization is the process of electrically charging an atom or molecule
by adding or removing electrons. Ions can be positive (when they lose
one or more electrons) or negative (when they gain one or more electrons).
A gas is considered ionized when some or all the atoms or molecules
contained in it are converted into ions. Plasma is an electrically neutral
gas in which all positive and negative charges—from neutral atoms, negatively
charged electrons, and positively charged ions—add up to zero. Plasma
exists everywhere in nature; it is designated as the fourth state of
matter (the others are solid, liquid, and gas). It has some of the properties
of a gas but is affected by electric and magnetic fields and is a good
conductor of electricity. Plasma is the building block for all types
of electric propulsion, where electric and/or magnetic fields are used
to push on the electrically charged ions and electrons to provide thrust.
Examples of plasmas seen every day are lightning and fluorescent light