Twenty-Six New Elements

The first of the new elements synthesized beyond uranium, the heaviest natural element, was neptunium. The synthetic atoms are radioactive, decaying into lighter elements, often within milliseconds. In general, the heavier the element, the shorter its half-life. For decades researchers have been trying to cross a sea of short-lived elements to find the “island of stability,” where “magic numbers” of protons and neutrons might combine to make superheavy atoms that last long enough to be studied.

Bar height and color indicate the half-life of the most long-lived isotope.

Island of stability Home of super- heavy elements lasting years

Year of recognition

x

Magic and Doubly Magic Numbers

Physicists theorize that protons and neutrons occupy separate series of shells in an atomic nucleus. A magic number of either particle is one that just fills all its shells. That gives a nucleus extra strength to resist the forces that tend to tear it apart. A doubly magic nucleus—say, 114 protons and 184 neutrons—is expected to be superstable even though it’s superheavy.

x

isotopes are variants of the same element, each with a different number of neutrons.

x

A joint committee of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP) certifies the synthesis of new elements. Elements 113, 115, 117, and 118 are under review by IUPAC and are referred to by their placeholder names until certified and officially named.

93

Np

Neptunium
x
Element
Number
  93
Atomic
Mass
  237
Half-
Life
  2.1 million years

False claims and failed attempts preceded the synthesis of neptunium by Edwin McMillan and Philip Abelson in 1940, including that of Enrico Fermi, who attempted to synthesize elements 93 and 94 but instead unknowingly discovered nuclear fission. Traces of neptunium have since been found in nature.

CREATOR: Lawrence Berkeley National Laboratory

94

Pu

Plutonium
x
Element
Number
  94
Atomic
Mass
  239
Half-
Life
  80 million years

Plutonium was synthesized, by bombarding uranium with deuterons, in 1940 but concealed until 1946 because of World War II. It was named for the dwarf planet Pluto. Co-discoverer Glenn Seaborg proposed the symbol “Pu” as a joke, which was accepted without question.

CREATOR: Lawrence Berkeley National Laboratory

95

Am

Americium
x
Element
Number
  95
Atomic
Mass
  243
Half-
Life
  7,370 years

Scientists at Berkeley synthesized americium in 1944 by bombarding plutonium with high-energy neutrons. Americium and curium were closely tied to the Manhattan Project. Their discovery was revealed in 1945, when co-discoverer Glenn Seaborg broke the news as a guest on Quiz Kids, a radio game show for children with high IQs.

CREATOR: Lawrence Berkeley National Laboratory

96

Cm

Curium
x
Element
Number
  96
Atomic
Mass
  247
Half-
Life
  15.6 million years

Scientists at Berkeley synthesized curium in 1944 by sending helium nuclei into plutonium. Its name, honoring Pierre and Marie Curie, was among suggestions solicited for element 95 during Glenn Seaborg’s appearance on the radio show Adventures in Science. Earlier, co-discoverer Tom Morgan had dubbed it and americium “delirium” and “pandemonium” after the group’s laborious discovery.

CREATOR: Lawrence Berkeley National Laboratory

97

Bk

Berkelium
x
Element
Number
  97
Atomic
Mass
  247
Half-
Life
  1,380 years

Scientists at Berkeley synthesized berkelium in 1950 by bombarding americium with helium ions. It was named for its birthplace in the pattern of terbium, the element above it on the periodic table. Terbium and three other elements were named for Ytterby, the small but mineral-rich Swedish village where they were discovered.

CREATOR: Lawrence Berkeley National Laboratory

98

Cf

Californium
x
Element
Number
  98
Atomic
Mass
  251
Half-
Life
  898 years

Scientists at Berkeley synthesized californium in 1950 by bombarding curium with helium ions. Californium took its name from the state and the University of California. This broke from the naming convention for recently discovered elements, whose names were connected to the elements above them on the periodic table.

CREATOR: Lawrence Berkeley National Laboratory

99

Es

Einsteinium
x
Element
Number
  99
Atomic
Mass
  252
Half-
Life
  471.7 days

Einsteinium was discovered in the debris of the first thermonuclear weapons test, code-named “Mike,” which the United States detonated in 1952 in Enewetak, an atoll in the South Pacific. Scientists working under Albert Ghiorso confirmed the discovery of the new element on filter papers that were flown on an airplane through the explosion cloud.

CREATOR: University of California Radiation Laboratory, Argonne National Laboratory, Los Alamos National Laboratory

100

Fm

Fermium
x
Element
Number
  100
Atomic
Mass
  257
Half-
Life
  100.5 days

Fermium, named for Enrico Fermi, was discovered in 1952 in the debris of the first thermonuclear weapons test, code-named “Mike,” on the Enewetak Atoll in the South Pacific. Scientists under Albert Ghiorso isolated the element from radioactive debris on coral brought from a nearby island.

CREATOR: University of California Radiation Laboratory, Argonne National Laboratory, Los Alamos National Laboratory

101

Md

Mendelevium
x
Element
Number
  101
Atomic
Mass
  258
Half-
Life
  51.5 days

Scientists at Berkeley synthesized mendelevium in 1958 by bombarding einsteinium with helium ions. Seeking to name it after Dmitry Mendeleyev, creator of the periodic table, co-discoverer Glenn Seaborg had to persuade the United States government to allow a proposal for a Russian scientist during the Cold War.

CREATOR: Lawrence Berkeley National Laboratory

102

No

Nobelium
x
Element
Number
  102
Atomic
Mass
  259
Half-
Life
  58 minutes

Scientists at the Nobel Institute of Physics in Stockholm named nobelium in 1957, but their work was later found to be in error. Discovery credit was granted to scientists at Dubna, who synthesized the element in 1965 through bombarding curium with a carbon isotope. They kept the name.

CREATOR: Joint Institute for Nuclear Research

103

Lr

Lawrencium
x
Element
Number
  103
Atomic
Mass
  262
Half-
Life
  4 hours

Scientists at Berkeley and Dubna synthesized lawrencium in the 1960s. Credit was deemed “impossible to say other than that full confidence was built up over a decade with credit attaching to work in both Berkeley and Dubna,” and was given in 1971. Berkeley scientists supported this compromise, while in the same document contesting other IUPAC decisions.

CREATOR: Lawrence Berkeley National Laboratory, Joint Institute for Nuclear Research

104

Rf

Rutherfordium
x
Element
Number
  104
Atomic
Mass
  263
Half-
Life
  10 minutes

In the 1960s scientists at Berkeley and Dubna each produced rutherfordium and attempted to name it. The International Union of Pure and Applied Chemistry split credit. The Americans then criticized the IUPAC and Russian claim, stoking the naming controversy. Credit remains shared, and in 1997 the IUPAC finally approved a name honoring Ernest Rutherford.

CREATOR: Lawrence Berkeley National Laboratory, Joint Institute for Nuclear Research

105

Db

Dubnium
x
Element
Number
  105
Atomic
Mass
  268
Half-
Life
  32 hours

Scientists at Dubna and Berkeley share credit for dubnium, an element that remained unnamed for 27 years. In 1997 the IUPAC resolved the naming of elements 101 to 109, under which it recommended dubnium because the Berkeley lab had been credited similarly “on more than one occasion.”

CREATOR: Joint Institute for Nuclear Research, Lawrence Berkeley National Laboratory

106

Sg

Seaborgium
x
Element
Number
  106
Atomic
Mass
  271
Half-
Life
  2.4 minutes

Scientists at Berkeley discovered seaborgium in 1974 by bombarding californium with oxygen ions. A 1994 rule that no element can be named for a living person involved it in a controversy over elements 104 to 106. It was briefly named rutherfordium. Seaborgium was accepted in 1997, two years before Glenn Seaborg’s death.

CREATOR: Lawrence Berkeley National Laboratory

107

Bh

Bohrium
x
Element
Number
  107
Atomic
Mass
  270
Half-
Life
  1 minute

Scientists at Darmstadt synthesized bohrium in 1981 by bombarding bismuth with chromium ions. Russian scientists had proposed nielsbohrium, after Niels Bohr, for element 105. After much debate it was shortened and given to element 107, as part of a 1997 resolution to a debate over several element names.

CREATOR: Joint Institute for Nuclear Research, GSI Helmholtz Center for Heavy Ion Research

108

Hs

Hassium
x
Element
Number
  108
Atomic
Mass
  270
Half-
Life
  22 seconds

Scientists at Darmstadt synthesized hassium in 1984 by bombarding atoms of lead with ions of iron. The element’s name comes from Hassia, the Latin version of the German state of Hessen, where it was first produced. It was named in 1997 as part of a resolution to a debate over several element names.

CREATOR: GSI Helmholtz Center for Heavy Ion Research

109

Mt

Meitnerium
x
Element
Number
  109
Atomic
Mass
  278
Half-
Life
  8 seconds

Scientists at Darmstadt synthesized meitnerium in 1982 by bombarding bismuth with iron ions. Its namesake is Lise Meitner, an Austrian and Swedish physicist who co-discovered nuclear fission but was famously omitted from the Nobel Prize.

CREATOR: GSI Helmholtz Center for Heavy Ion Research

110

Ds

Darmstadtium
x
Element
Number
  110
Atomic
Mass
  281
Half-
Life
  20 seconds

Scientists at Darmstadt synthesized darmstadtium in 1995 through the bombardment of lead atoms with nickel ions. It was named for Darmstadt, the city in Germany where it was discovered.

CREATOR: GSI Helmholtz Center for Heavy Ion Research

111

Rg

Roentgenium
x
Element
Number
  111
Atomic
Mass
  281
Half-
Life
  26 seconds

Scientists at Darmstadt synthesized roentgenium by bombarding bismuth with ions of nickel. They named it for Wilhelm Conrad Röntgen, the German scientist who discovered the x-ray and was awarded the first Nobel Prize in physics, in 1901.

CREATOR: GSI Helmholtz Center for Heavy Ion Research

112

Cn

Copernicium
x
Element
Number
  112
Atomic
Mass
  285
Half-
Life
  30 seconds

Scientists at Darmstadt synthesized copernicium in 1996 and confirmed their work over the following decade. They named it to honor 16th-century astronomer Nicolaus Copernicus and to highlight the link between astronomy and chemistry, specifically the analogy between the planets orbiting the sun and electrons orbiting an atomic nucleus.

CREATOR: GSI Helmholtz Center for Heavy Ion Research

113

Uut

Ununtrium
x
Element
Number
  113
Atomic
Mass
  286
Half-
Life
  20 seconds

Scientists at Dubna and at Wako near Tokyo both announced the production of ununtrium in 2004, but the findings did not meet the criteria for discovery. The element retained its placeholder name meaning “one-one-three.” In 2012, Japanese scientists announced they had successfully confirmed their original 2004 work.

CREATOR: Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory, RIKEN Nishina Center for Accelerator Based Science

114

Fl

Flerovium
x
Element
Number
  114
Atomic
Mass
  289
Half-
Life
  2.7 seconds

Flerovium was synthesized in 2004 by a collaboration of scientists at Dubna and Livermore through the fusion of plutonium and calcium. It was named for Georgy Flerov, a pioneer of work in uranium fission and heavy-ion physics and a co-founder of the Dubna laboratory where flerovium was first produced.

CREATOR: Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory

115

Uup

Ununpentium
x
Element
Number
  115
Atomic
Mass
  289
Half-
Life
  220 milliseconds

Scientists at Dubna, Livermore, and Wako have claims for the synthesis of element 115. No claims have met the criteria for discovery yet, but some are under review. Until discovery is recognized, the element has only a placeholder name meaning “one-one-five.”

CREATOR: Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory, RIKEN Nishina Center for Accelerator Based Science

116

Lv

Livermorium
x
Element
Number
  116
Atomic
Mass
  291
Half-
Life
  53 milliseconds

A collaboration of scientists from Dubna and Livermore confirmed synthesis of livermorium in 2004 by bombarding curium with calcium ions. The discovery was undisputed, and the element was named for Lawrence Livermore National Laboratory in California.

CREATOR: Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory

117

Uus

Ununseptium
x
Element
Number
  117
Atomic
Mass
  294
Half-
Life
  80 milliseconds

A collaboration of scientists from Dubna and Dimitrovgrad in Russia and Livermore, Oak Ridge, Vanderbilt, and Las Vegas in the United States claimed synthesis of element 117 in 2010 by bombarding berkelium with calcium ions. The claim is under review. Until discovery is recognized, the element has only a placeholder name meaning “one-one-seven.”

CREATOR: Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory

118

Uuo

Ununoctium
x
Element
Number
  118
Atomic
Mass
  294
Half-
Life
  0.89 millisecond

A collaboration of scientists from Dubna and Livermore claimed synthesis in 2006 via the bombardment of californium with calcium ions, but the findings did not meet the criteria for discovery. New claims are under review. Until discovery is recognized, the element has only a placeholder name meaning “one-one-eight.”

CREATOR: Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory

John Tomanio, NGM Staff; Tony Schick
Consultants: Paul Karol, Carnegie Mellon University; Roger Henderson, Lawrence Livermore National Laboratory

Sources: International Union of Pure and Applied Chemistry; National Nuclear Data Center, Brookhaven National Laboratory