The Physics
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Density of Plutonium

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Bibliographic Entry Result
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Emsley, John. The Elements. Clarendon Press 3rd ed, 1998: 156-7 "Density kg/m3: 19,840 (a) [298 K]: 16,623 liquid at M.p." 19,840 kg/m3
16,623 kg/m3
Gagnon, Steve. It's Elemental: Plutonium. Jefferson National Accelerator Facility, 22 May 2004. "Density: 19.84 grams per cubic centimeter" 19,840 kg/m3
Mass, Weight, Density or Specific Gravity of Different Metals. SI-Metric, 9 December 2003.
Metal or alloy kg/cu.m
plutonium 19800
19,800 kg/cu.m
Winter, Mark. Plutonium. Webelements, 22 May 2004. "Density of solid [kg m-3]: 19816" 19,816 kg/m3

The element plutonium was first created by Glenn Seaborg in 1940. Named for the planet Pluto, plutonium was the second transuranium element to be discovered. On the periodic table of elements, Plutonium is abbreviated Pu and has the atomic number 94 because it contains 94 protons in its nucleus. It is the fifth element in the actinide series.

The metal plutonium has a silvery appearance and becomes yellow when exposed to air. At present, there are fifteen different isotopes of plutonium and each isotope is distinguished by its unique atomic mass (atomic mass is the sum mass of the protons and neutrons). The isotope number is written after the element abbreviation (ex-isotope 238 is written Pu-238).

The first isotope of Plutonium, Pu-238, was created by bombarding uranium with deuterons in a cyclotron at Seaborg's lab in California and the second, Pu-239 was created in a similar fashion by Seaborg, in 1941. Of the isotopes, Pu-239 is considered most valuable for it can be used as fuel in nuclear reactors and nuclear weapons. Plants in Russia and former Soviet republics use Pu-239 to generate electrical power, however, this is done at considerable risk for the element plutonium is highly radioactive. (It has been shown that plutonium can be absorbed by human bone marrow for it emits alpha particles at a high rate).

All sources I found state the density of plutonium to be 19,800 kg/m3 in its solid form.

Hayley Miskiewicz -- 2004

Bibliographic Entry Result
(w/surrounding text)
Plutonium Crystal Phase Transitions. Weapons of Mass Destruction (WMD). 27 April 2005. "Plutonium is a unique element in exhibiting six different crystallographic phases at ambient pressure (it has a seventh phase under pressure). The densities of these vary from 16.00 to 19.86 g/cm3." 16,000–19,860 kg/m3
"The plutonium in the first American atomic bombs was stabilized in the low density delta phase (density 16.9) by alloying it with 3% gallium (by molar content, 0.8% by weight), but was otherwise of high purity. The advantages of using delta phase plutonium over using the high density alpha phase (density 19.2), which is stable in pure plutonium below 115 degrees C, are that the delta phase is malleable while the alpha phase is brittle, and that delta phase stabilization prevents the dramatic shrinkage during cooling that distorts cast or hot-worked pure plutonium."

Editor's Supplement -- 2006