These 48 stable nuclides, stabilized by their even numbers of paired neutrons, form most of the stable isotopes of the odd-numbered elements; the very few odd–odd nuclides comprise the others. There are 41 odd-numbered elements with Z = 1 through 81, of which 30 (including hydrogen, since zero is an even number) have one stable odd-even isotope, the elements technetium (43 Tc) and promethium (61 Pm) have no stable isotopes, and nine elements: chlorine (17 Cl), potassium (19 K), copper (29 Cu), gallium (31 Ga), bromine (35 Br), silver (47 Ag), antimony (51 Sb), iridium (77 Ir), and thallium (81 Tl), have two odd–even stable isotopes each. This makes a total of 30×1 + 9×2 = 48 stable odd–even isotopes. The lightest example of this type of nuclide is 1 H (protium) as zero is an even number while the heaviest example is 81 Tl. There are also five primordial long-lived radioactive odd–even isotopes, 37 Rb, 49 In, 75 Re, 63 Eu, and 83 Bi. The last two were only recently found to undergo alpha decay, with half-lives greater than 10 years.