Superheavy Elements

Stable Superheavy Element found in Nature?

This post discusses the chemistry of stable superheavy elements in nature (i.e., not artificially created in nuclear reactions or accelerators). To date none have been found on Earth, though scientists and geologists have searched the world over for the past half century. However, in my novel Copernicium-296 I imagine a superheavy element found on a planet near Earth (36 lightyears distant). The novel posits that a stable superheavy element found on that planet can be a basis for harvesting quantum energy from the vacuum of space.

One model of the atomic nucleus postulates a shell structure inside the nucleus similar to electron shells in an atom. The nucleus shells are sequentially filled in with nucleons (protons and neutrons) for successively larger nuclei. That is,elements and their isotopes in the Periodic Table. An element with an isotope that has a filled shell has unique properties. One of these is increased stability against radioactive disintegration. A filled shell is denoted by “magic numbers” for the number of nucleons in the shell. Nucleons refer to protons, denoted Z, and neutrons, denoted N. The total nucleons in a nucleus is the isotope’s mass number, denoted A. It is the sum, Z+N [A = Z + N]).

Magic Numbers Show Which Isotopes are Stable

In a filled shell, the number of nucleons is called a magic number. A magic number can be associated with Z, N, or A in the filled shell. The known magic numbers are 2, 8, 20, 28, 50, 82, and 126. Any element that has a Z, N, or A equal to a magic number is more stable than its neighbors. For example, tin (Z = 50), has 10 stable isotopes, whereas indium (Z = 49) and antimony (Z = 51) have only 2 stable isotopes each. The numbers 114 and 184 may also be magic numbers, though this remains unproven. A particular case of stability is observed when both Z + N is magic numbers.

Image Source

Magic Numbers for Stable Superheavy Elements

For the so-called superheavy elements (Z>103), none of the ones that have been synthesized so far are stable. Only one, Flerovium (Z = 114) has a “magic number” of protons. But N for the known isotopes of Flerovium is not a magic number, nor is A. As it is, all the known superheavy elements have isotopes with half-lives of weeks, hours, seconds, even milliseconds. If any of these were created in the Big Bang (14 billion years ago) there would be none to be found today, having decayed to nothing long ago.

Current theory predicts that a super-heavy element with both Z and N equal to magic numbers, or near those numbers, would be stable. As well, super-heavy elements with Z and N “near” those magic numbers would be stable. This predicted group of elements has been given the moniker “Island of Stability.” A few isotopes of Copernicium (Z=112, which is “near” the magic 114) have been synthesized in high energy accelerators, but with nowhere near 184 neutrons. If an isotope of Copernicium with 184 neutrons were to be synthesized, or found in nature, it might be stable (i.e., its N is a magic number and its Z is “near” a magic number).

Stable Isotope in Island of Stability

In my Science Fiction novel, Copernicium-296, a key underlying plot element is the discovery of an isotope of Copernicium with 184 neutrons. The plot imagines that this isotope is a stable super-heavy element in nature. If not stable it would have to be very long-lived, or essentially stable. The number, 296, is the isotope’s mass number (A); that is, it the total number of nucleons in the nucleus (A=Z+N). In scientific literature the mass number of an isotope is often appended to its name or its symbol. For the Copernicium in my novel (Z=112) the mass number, A, is 296 (A=112+184=296), hence the name of the novel. A very long-lived isotope of Copernicium would be unusual and could turn out to be extremely valuable.