Heavy Elements
| Number | Names | when | Chemically like (bold if verified) |
| 92 | Uranium (U) | natural | IIIa Neodymium |
| 93 | Neptunium (Np) | natural | IIIa Promethium |
| 94 | Plutonium (Pu) | 1940 | IIIa Samarium |
| 95 | Americium (Am) | 1944 | IIIa Europium |
| 96 | Curium (Cm) | 1944 | IIIa Gadolinium |
| 97 | Berkelium (Bk) | 1949 | IIIa Terbium |
| 98 | Californium (Cf) | 1950 | IIIa Dysprosium |
| 99 | Einsteinium (Es) | 1952 | IIIa Holmium |
| 100 | Fermium (Fm) | 1953 | IIIa Erbium |
| 101 | Mendelevium (Md) | 1955 | IIIa Thulium |
| 102 | Nobelium (No) | 1958 | IIIa Ytterbium |
| 103 | Lawrencium (Lr) | 1961 | IIIa Lutetium (and Yttrium, Scandium by some charts) |
| 104 | Unnilquadium (Unq)
Dubnium (Db) Rutherfordium (Rf) | 1964 | 4 IVa Hafnium, Zirconium, Titanium |
| 105 | Unnilpentium (Unp)
Joliotium (Jl) Hahnium (Ha) Nielsbohrium Dubnium (Db) | 1968 | 5 Va Tantalum, Niobium, Vanadium |
| 106 | Unnilhexium (Unh)
Rutherfordium (Rf) Seaborgium (Sg) | 1974 | 6 VIa Tungsten, Molybdenum, Chromium |
| 107 | Unnilseptium (Uns)
Nielsbohrium (Ns) Bohrium (Bh) | 1981 | 7 VIIa Rhenium, Technitium, Manganese |
| 108 | Unniloctium
Hahnium (Ha or Hn) Hassium (Hs) | 1984 | 8 VIIIa Osmium, Ruthenium, Iron |
| 109 | Meitnerium (Mt)
Unnilennium (Une) | 1982 | 9 VIIIa Iridium, Rhodium, Cobalt |
| 110 | Darmstadtium (Ds)
Ununnilium (Uun) | 1994 | 10 VIIIa Platinum, Palladium, Nickel |
| 111 | Roentgenium (Rg)
Unununium (Uuu) | 1994 | 11 Ib Gold, Silver, Copper |
| 112 | Ununbium (Uub) | 1996 | 12 IIb Mercury, Cadmium, Zinc |
| 113 | Ununtertium (Uut) | 13 IIIb Thallium, Indium, Gallium, Aluminum, Boron | |
| 114 | Ununquadium (Uuq) | 1998 | 14 IVb Lead, Tin, Germanium, Silicon, Carbon |
| 115 | Ununpentium (Uup) | 15 Vb Bismuth, Antimony, Arsenic, Phosphorus, Nitrogen | |
| 116 | Ununhexium (Uuh) | 1999 | 16 VIb Polonium, Tellurium, Selenium, Sulfur, Oxygen |
| 117 | Ununseptium (Uus) | 17 VIIb Astatine, Iodine, Bromine, Chlorine, Fluorine | |
| 118 | Ununoctium (Uuo) | 1999 | 18 VIIIb Radon, Xenon, Krypton, Argon, Neon, Helium |
Yes, the same names appear more than once in many cases. Elements were produced by different teams of scientists over the years, from different countries, and different names were suggested. It has been hard to form a consensus. For a while, the cold war played a role in perpetuating the disagreements. I found these names here:
http://www.britannica.com/bcom/eb/article/6/0,5716,75136,00.html
http://www.newton.dep.anl.gov/askasci/chem99/chem99246.htm
http://www.servtech.com/~whitfitz/elements.htm
Natural Occurrence of Transuranic Elements
At some point you probably "learned" that Uranium, element number 92, is the highest element on the periodic table that occurs in nature. Not true — neptunium and plutonium occur naturally. They are found in trace quantities in uranium ore. The neptunium is created when a neutron given off by a U-238 nucleus hits another uranium nucleus creating U-239, which then beta-decays to Np-239. The half-life of Np-239 is about 2 days, it then beta-decays into Pu-239. Thus, wherever U-238 occurs in sufficient concentrations, Np-239 and Pu-239 also occur, and if you consider the first to be a natural element then the others must be too. (U-238 is naturally occurring because the universe isn't old enough yet.)
Due to similar effects, it is even possible that a stray atoms of even heavier elements (such as americium) are created from time to time, only to decay again before anyone can detect them. Also, of course, there are scads of heavy isotopes that occur naturally during supernova explosions, only to disappear milliseconds later.
If you use "non-radioactive isotope" as the definition of a naturally-occurring isotope, then Uranium does not count as a naturally occurring element because all of its isotopes decay. (The most stable isotope is U-238 with a half life of 4 billion years. Uranium occurs in nature because its half-life is so long.)
In the early 1960's it was thought that the "shell effects" that cause the neuclei He-4, O-16, Ca-40, Ca-48 and Pb-208 to be so stable, would also occur for Uuq-298 (which at the time was called simply element 114). It was even thought that isotopes near Uuq-298 might be stable enough to not decay at all. By the early 1980's it was established that there are no stable isotopes near Uuq-298 and that the heavy elements are difficult to produce.
However, a lighter isotope of element 112 has been shown to have a half-life of about 5 minutes (see this page). It has even been verified to have "adsorption" properties, like Mercury.
This page was written in the "embarrassingly readable" markup language RHTF, and was last updated on 2011 Jan 20.
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