The heaviest elements
Part of the chart of nuclides showing the isotopes of elements that are heavier than californium (Z = 98). The number of protons (the atomic number, Z) increases along the y-axis, and the number of neutrons (N) increases along the x-axis. Isotopes produced in cold-fusion reactions with lead-208 and bismuth-209 targets are shown inside the oval-shaped white line on the left, while those created in hot-fusion reactions with calcium-48 projectiles are shown inside the white line to the right. The different decay modes are indicated by different colours: nuclei that decay via alpha emission are shown in yellow, while those that undergo spontaneous fission are shown in green. Nuclides can also undergo beta decay (blue), electron capture (pink) or gamma emission (white). The lifetimes given are for the dominant decay mode (where "a" denotes years). The blue contours show the contribution of the shell effect to the nuclear binding energy: the darker the colour, the greater the shell effect. In the vicinity of closed shells (dark areas) the nuclei undergo alpha decay (yellow squares and light-blue arrows) which results in a nucleus that is two protons and two neutrons lighter than its parent. As the daughter nuclei get further away from the magic numbers Z = 108, N = 162 and Z = 114, N = 184 spontaneous fission becomes more probable, and at the boundaries of the "islands of stability" a nuclide may undergo both decay modes. For odd?odd nuclei - such as the isotope 288115 and its daughter products with Z = 113, 111, 109 and so on - alpha decay dominates down to the isotope dubnium-268 (Z = 105), which then undergoes spontaneous fission after about one day.