(Formula done in Microsoft Word)

where K is the electrostatic constant, r is the distance between the two particles (electron and nucleus, in this case), and the two q's are the charges of the particles. This formula is very basic, and only deals with particles as points (spherical cow physics at it's finest). In order to get the electrons to break free from their orbits around the nucleus of an atom, an outside force must act upon the system to effectively "break" the attractive force that already exists. To overcome this bond, there needs to be a steady supply of energy, whether it's electric, electromagnetic, or thermal, to heat things up. If the supply of energy is cut off or is insufficient, then the electrons and positive ions can reform into atoms and molecules once again. In general, gases turn into plasma when the temperature is around 1000 Kelvins, or 726.85 degrees Celsius. Professor William Howard from the University of Alaska, Fairbanks notes that plasma can also be made by heating an ionic solid, but for our purposes, we will be focusing on plasmas that are made from a gaseous state. Here's a neat diagram showing some different plasmas and the temperatures they form at: