Plutonium

Plutonium

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melting point: 640°C
boiling point: 3,228°C
density: 19.84g/cm ³
most common ions: Pu ³⁺, Pu ⁴⁺, PuO ₂⁺, PuO ₂²⁺, PuO ₅³⁻

Plutonium was discovered by Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl in 1940. They prepared a new isotope of neptunium, ²³⁸Np, which decayed by β -emission to ²³⁸Pu.

Their work as part of the Manhattan Project was kept secret and was finally reported in 1946, after World War II, although the existence of plutonium had been revealed to the world earlier, when the atomic bomb was dropped over Nagasaki, Japan. There are sixteen isotopes of plutonium, having mass numbers ranging from 232 to 247. The principal isotopes of Pu are those having mass numbers 238, 239, 240, 241, 242, and 244. Ton quantities of ²³⁹Pu (having a half-life of 2.4 × 0⁴ y) are available. The isotope ²³⁹Pu is the source material for nuclear weapons and is produced via neutron capture reactions on ²³⁸U in nuclear reactors.

About 110 tons of ²³⁹Pu are generated in nuclear power plants each year, with approximately 40 percent of the energy produced in the nuclear fuel cycle coming from ²³⁹Pu. About three times as much electricity is generated from ²³⁹Pu in the United States as from oil-fired electrical generating plants. The ground state (outer orbital) electronic configuration of Pu is [Rn]5f ⁶7s ². The most stable oxidation state for plutonium ions in solution is +4, although appreciable amounts of plutonium in its +3, +5, and +6 oxidation states can exist. The aqueous chemistry of plutonium is further complicated by the successive, stepwise hydrolysis of Pu(IV) compounds to form polymers of colloidal dimensions. Plutonium is the transuranium element that is most abundant in the environment, due to the atmospheric testing of nuclear weapons during the 1950s and 1960s that deposited approximately 4.2 tons of plutonium in the environment. Most of this plutonium is in the soil, in which it has no discernable effects.

see also Actinium; Berkelium; Einsteinium; Fermium; Lawrencium; Mendelevium; Neptunium; Nobelium; Protactinium; Rutherfordium; Seaborg, Glenn Theodore; Thorium; Uranium.

Walter Loveland

Bibliography

Seaborg, Glenn T., and Loveland, Walter (1990). The Elements beyond Uranium. New York: Wiley.