Illustrated Glossary of Organic Chemistry

Unionized: A substance that has not formed ions. Does not mean "Has not formed a union." Jimmy Hoffa has nothing to do with this term in chemistry.

Before leaving group departure: molecule is unionized.		After leaving group departure: molecule has been ionized.

At the start of an S_N1 reaction, tert-butyl iodide is unionized. All atoms are covalently bonded, and there are no ions. In the S_N1 rate-determining step, the carbon-iodine bond suffers heterolytic cleavage, forming a tert-butyl carbocation (blue) and iodide anion (the leaving group; in red). The molecule is now ionized.