Transcript Slide 1

By Sean Byrne
The production of plutonium and neptunium by
bombarding uranium-238 with neutrons was
predicted in 1940 by two teams working
independently.
Plutonium was first produced and isolated on
February 23, 1941 by deuteron bombardment of
uranium in the 60-inch cyclotron at Berkeley.
The discovery was kept secret due to the war. It
was named after Pluto, having been discovered
directly after neptunium.
Glenn Seaborg
General
Physical properties
Name, Symbol,
Number
plutonium, Pu, 94
Chemical series
actinides
Group, Period, Block
n/a, 7, f
Appearance
silvery white
−1
Standard atomic
weight
(244) g·mol
Electron configuration
[Rn] 5f 7s
Electrons per shell
2, 8, 18, 32, 24, 8, 2
6
2
Phase
solid
Density (near r.t.)
19.816 g·cm
Liquid density at m.p.
16.63 g·cm
Melting point
912.5 K
(639.4 °C, 1182.9 °F)
Boiling point
3505 K
(3228 °C, 5842 °F)
Heat of fusion
2.82 kJ·mol
Heat of vaporization
333.5 kJ·mol
Heat capacity
(25 °C) 35.5
−1 −1
J·mol ·K
−3
−3
−1
−1
244Pu
is the nucleon-richest atom that naturally occurs in the
Earth's crust.
Plutonium has been called "the most complex metal" and "a
physicist's dream but an engineer's nightmare"for its peculiar
physical and chemical properties.
It has six allotropes normally and a seventh under pressure,
each of which have very similar energy levels but with
significantly varying densities, making it very sensitive to
changes in temperature, pressure, or chemistry, and allowing
for dramatic volume changes following phase transitions
The most significant isotope of plutonium is 239Pu .
All 15 plutonium isotopes are radioactive, and most emit relatively
weak alpha radiation which can be blocked even by a sheet of
paper.
The main isotopes of plutonium are:
Pu-238,
Pu-239,
Pu-240,
Pu-241,
Pu-242,
(half-life 88 years, alpha decay)
fissile (half-life 24 000 years, alpha decay)
fertile (half-life 6 560 years, alpha decay)
fissile (half-life 14.3 years, beta decay)
(half-life 376 000 years, alpha decay)
Pluto was considered to be a planet at the time (though technically
it should have been "plutium", Seaborg said that he did not think it
sounded as good as "plutonium"). Seaborg chose the letters "Pu" as
a joke, which passed without notice into the periodic table.
The isotope 239Pu is a key fissile
component in nuclear weapons, due to
its ease of fissioning and availability. The
critical mass for an unreflected sphere of
plutonium is 16 kg, but through the use
of a neutron-reflecting tamper the pit of
plutonium in a fission bomb is reduced to
10 kg.
Complete detonation of plutonium will
produce an explosion equivalent to the
explosion of 20 kilotons of trinitrotoluene
(TNT) per kilogram.
Hanford Site plutonium production
reactors along the Columbia River
during the Manhattan Project.
The isotope plutonium-238 (238Pu) has a half-life of 88 years
and emits a large amount of thermal energy as it decays.
These characteristics make it well suited for safe electrical
power generation for devices which must function without
direct maintenance for timescales approximating a human
lifetime. It is therefore used in radioisotope thermoelectric
generators such as those powering the Cassini and New
Horizons (Pluto) space probes. 238Pu has been used
successfully to power artificial heart pacemakers, to reduce
the risk of repeated surgery. It has been largely replaced by
lithium based primary cells, but as of 2003 there were
somewhere between 50 and 100 plutonium-powered
pacemakers still implanted and functioning in living patients.
It displays five ionic oxidation states in aqueous solution:
• Pu(III), as Pu3+ (blue lavender)
• Pu(IV), as Pu4+ (yellow brown)
• Pu(V), as PuO2+ (thought to be pink; this ion is unstable in solution and will
disproportionate into Pu4+ and PuO22+.)
• Pu(VI), as PuO22+ (pink orange)
• Pu(VII), as PuO52- (dark red); the heptavalent ion is rare and prepared only
under extreme oxidizing conditions.
Plutonium reacts readily with oxygen, forming PuO and PuO2, as well as
intermediate oxides. It reacts with the halogens, giving rise to compounds such
as PuX3 where X can be F, Cl, Br or I; PuF4 and PuF6 are also seen. The following
oxyhalides are observed: PuOCl, PuOBr and PuOI. It will react with carbon to
form PuC, nitrogen to form PuN and silicon to form PuSi2.
Plutonium reacts readily with oxygen, forming PuO and PuO2, as well as
intermediate oxides. It reacts with the halogens, giving rise to compounds such
as PuX3 where X can be F, Cl, Br or I.
The following oxyhalides are observed: PuOCl, PuOBr and PuOI. It will react with
carbon to form PuC, nitrogen to form PuN and silicon to form PuSi2.
Plutonium like other actinides readily forms a dioxide plutonyl core (PuO2). In the
environment, this plutonyl core readily complexes with carbonate as well as other
oxygen moieties (OH-, NO2-, NO3-, and SO4-2) to form charged complexes which
can be readily mobile with low affinities to soil.
PuO2(CO3)1-2
PuO2(CO3)2-4
PuO2(CO3)3-6
PuO2 Plutonium also readily shifts valences between the +3, +4, +5 and +6
states. It is common for some fraction of plutonium in solution to exist in all of
these states in equilibrium.