Naturally occurring chromium (24Cr) is composed of four stable isotopes; 50Cr, 52Cr, 53Cr, and 54Cr with 52Cr being the most abundant. Twenty-two radioisotopes, all synthetic, have been characterized, the most stable being 51Cr with a half-life of 27.70 days. All of the remaining radioactive isotopes have half-lives less than a day and for the majority of these less than a minute. This element also has two very short-lived meta states: 45mCr and 59mCr.