Symbol: Pu
Atomic number: 94
Category: actinides
Group: n/a
Period: 7
Block: f
Atomic weight: (244) g/mol
Electrons per shell: 2, 8, 18, 32, 24, 8, 2
CAS number: 7440-07-5
Phase: solid
Density: 19.816 kg/dm3 (near room temperature)
Melting point: 912.5 K (639.4 °C, 1182.9 °F)
Boiling point: 3505 K (3228 °C, 5842 °F)
Crystal structure: monoclinic
Oxidation states: 3, 4, 5, 6
Electronegativity: 1.28 (Pauling scale)
Name's origin: Pluto
Name's meaning: the planet in the Solar System
Facts:
- has a bright silvery appearance at first, much like nickel, but it oxidizes very quickly to a dull gray, although yellow and olive green are also reported
- is about as hard and brittle as grey cast iron unless it is alloyed with other metals
- is not a good conductor of heat or electricity
- has six allotropes, from alpha- to zeta- plutonium
- has wenty radioactive isotopes, of which the longest-lived is plutonium-244, with a half-life of 80.8 million years
- the most important isotope of plutonium is plutonium-239, with a half-life of 24100 years
- when exposed to moist air, it forms oxides and hydrides that expand the sample up to 70% in volume, which in turn flake off as a powder that can spontaneously ignite
- is used in nuclear weapons and use in some nuclear reactors
- is also a radioactive poison that accumulates in bone marrow
- reacts with carbon, halogens, nitrogen and silicon