Naturally-Occurring and Synthetic Elements

1A 2A 3A 4A 5A 6A 7A 8A
(1) (2) (13) (14) (15) (16) (17) (18)
3B 4B 5B 6B 7B 8B 1B 2B
(3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
1 H He
2 Li Be B C N O F Ne
3 Na Mg Al Si P S Cl Ar
4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
6 Cs Ba La   Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
7 Fr Ra Ac   Rf Db Sg Bh Hs Mt Ds Rg Uub Uuq
6   Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
7   Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

  

Key:   naturally-occurring   synthetic

 

Elements 1 through 92 (except for elements 43 and 61) occur naturally on Earth, although some are only present in extremely small quantities.

Element 43, Technetium (Tc), is unstable, and all of its isotopes have relatively short half-lives, ranging from 4.2 million years (98Tc) to 5.0 seconds (108Tc).  A half-life of 4.2 million years may sound like a long time, but since the Earth is 4.5 billion years old, all of the technetium that was originally present in the crust has decayed by now.  Technetium has been detected in the corona of some stars, and can be produced artificially in kilogram quantities by the neutron bombardment of molybdenum-98, which forms technetium-99 by beta emission:

9842Mo  +  10n  —>  9942Mo  —>  9943Tc  +  0-1ß

 

Element 61, Promethium (Pm), is also unstable.  The most stable isotope of the element, promethium-145, has a half-life of 17.7 years; promethium-146 has a half-life of only 5.53 years, while that of promethium-147 is 2.62 years.  There are a number of other isotopes as well, but the majority of them have half-lives that are less than 30 seconds.  Promethium is found in trace amounts in uranium ores, but because it is so unstable, it never accumulates above the concentration of about a picogram (10-12 g) per ton of ore.  The spectral lines of promethium have also been observed in some stars.  Promethium can be produced artificially by the bombardment of neodymium-146 with neutrons to form neodymium-147, which decays into promethium-147 and a beta particle:

14660Nd  +  10n  —>  14760Nd  —>  14761Nd  +  0-1ß

 

The elements following uranium on the periodic table are only produced artificially, and are known as the transuranium or transuranic elements.  These elements may have existed on Earth early in its history, but like technetium, would have long ago decayed into more stable elements.  These elements can be produced by several processes:

  • neutron bombardment causes an element to absorb a neutron, thereby becoming a heavier isotope of that element; if this heavier isotope is unstable, it may undergo beta decay, in which a neutron is converted into a proton, with the emission of a beta particle (ß, a high-speed electron ejected from the nucleus).  The nucleus thus increases in atomic number by one unit: 

10n  —>  11p  +  0-1ß

  • fusion of heavy elements with lighter elements such as hydrogen, helium, carbon, nitrogen, or oxygen can be made to occur in cyclotrons and particle accelerators; the particles are brought together with just enough energy to overcome the mutual repulsion of the positively-charged nuclei and cause the elements to fuse together, forming a heavier element in their place. Sometimes this process is referred to as cold fusion (this has no relationship to the infamous "unlimited energy" "fusion-in-a-jar" cold fusion debacle of the late-1980's).  Some examples of this process are shown below:

24696Cm  +  126C  —>  254102No  +  4 10n

20983Bi  +  5826Fe  —>  266109Mt  +  10n

 

It has been theorized that the elements following element 112, which would be in the p-block region of the periodic table, might possibly be more stable than those of the last row of the transition metals (103-112); however, there is not as yet enough data to confirm whether this so-called "island of stability" actually exists.  In any case, since only a few million or (at best) billion of the heaviest of these atoms can be produced at any one time, it is rather doubtful that any major construction projects will use any of these elements as building materials! 

The table below lists the longest-lived isotopes of the transuranium elements, with their half-lives, discoverers, and method of production.*

 

Atomic
Number

Symbol

Name

Discoverer Year Named For ... Method of Production

Logest-lived
Isotope

Half-Life

93

Np

Neptunium

McMillan, Abelson 1940 the planet Neptune neutron bombardment of U-238 237 2,140,000 years

94

Pu

Plutonium

Seaborg, Wahl, Kennedy 1941 the planet Pluto beta-decay of Np-239 244 82,000,000 years

95

Am

Americium

Seaborg, James, Morgan, Ghiorso 1944 the American continent neutron bombardment of Pu-240 243 7,370 years

96

Cm

Curium

Seagorg, James, Giorso 1944 Marie & Pierre Curie alpha-particle bombardment of Pu-239 247 15,600,000 years

97

Bk

Berkelium

Thompson, Ghiorso, Seaborg 1949 Berkeley, California neutron bombardment of Cm-244 247 1,400 years

98

Cf

Californium

Thompson, Street, Ghiorso, Seaborg 1950 the state and University of California alpha-particle bombardment of Cm-242 251 890 years

99

Es

Einsteinium

Ghiorso, et. al. 1952 Albert Einstein neutron bombardment of Pu-239 254 275 days

100

Fm

Fermium

Ghiorso, et. al. 1952 Enrico Fermi neutron bombardment of U-238 257 101 days

101

Md

Mendelevium

Ghiorso, Harvey, Choppin, Thompson, Seaborg 1955 Dmitri Mendeleev, inventor of the periodic table alpha-particle bombardment of Es-253 258 56 days

102

No

Nobelium

Ghiorso, Sikkeland, Walton, Seaborg 1958 Alfred Nobel bombardment of Cm-246 with C-12 259 58 min

103

Lr

Lawrencium

Ghiorso, Sikkeland, Larsh, Latimer 1961 Ernest O. Lawrence, inventor of the cyclotron bombardment of Cf-250 with B-10 260 3 min

104

Rf

Rutherfordium

credit shared between scientists at Dubna, Russia, and Berkeley, CA 1964, 1969 Ernest Rutherford bombardment of Cf-249 with C-12, or Cm-248 with O-18 261 65 s

105

Db

Dubnium

credit shared between scientists at Dubna, Russia, and Berkeley, CA 1967, 1970 Dubna, Russia bombardment of Cf-249 with N-15, or Bk-249 with O-18 262 34 s

106

Sg

Seaborgium

Ghiorso, et. al. 1974 Glenn T. Seaborg bombardment of Cf-249 with O-18 271 2.4 min

107

Bh

Bohrium

Armbruster, Münzenberg, et. al. 1981 Niels Bohr cold fusion of Bi-209 and Cr-54 267 22 s

108

Hs

Hassium

Armbruster, Münzenberg, et. al. 1984 Hassias (L. for Hesse, the German state) cold fusion of Pb-208 and Fe-58 270 22 s

109

Mt

Meitnerium

Armbruster, Münzenberg, et. al. 1982 Lise Meitner, originator of the idea of nuclear fission cold fusion of Bi-209 and Fe-58 276 0.72 s

110

Ds

Darmstadtium

Rigol, et. al. 1994 Darmstadt, Germany, home of the Institute for Heavy Ion Research (GSI) bombardment of lead-208 with nickel-62 281 11.1 s

111

Rg

Roentgenium

Armbruster, Münzenberg, et. al. 1994 Wilhelm Röntgen, discoverer of X-rays fusion of bismuth-209 and nickel-64 280 3.6 s

112

Uub

Ununbiium

Institute for Heavy Ion Research (GSI) in Darmstadt, Germany 1996 n/a fusion of zinc-?? with lead-?? 283 5 min

114

Uuq

Ununquadium

JINR in Dubna, Russia 1998 n/a bombardment of plutonium-244 with calcium-48 288 2.8 s

* Data obtained from John Emsley, The Elements, 3rd ed.  Oxford, Clarendon Press, 1998; and David L. Heiserman, Exploring Chemical Elements and their Compounds.  New York:  TAB Books, 1992