Plutonium is a transuranic radioactive chemical element with symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states.
Three reasons Plutonium stands out
- 1
Highly radioactive, used in nuclear weapons and as a fuel in some reactors.
- 2
Less than 10 kilograms of it is sufficient to create a nuclear explosion.
- 3
The power source on both Voyager probes and the Curiosity Mars rover uses this element to generate heat and electricity.
A warm pellet for a cold, dark journey
Plutonium is famous for weapons and reactor fuel, but plutonium-238 has another identity. Its steady radioactive heat powers spacecraft traveling too far from the Sun for practical solar panels. Different isotopes have profoundly different nuclear roles, even though their chemistry is nearly identical.