Atomic number: 94

Symbol: Pu

Category: actinide 

Density at 25°C: solid: density: 19.816 g·cm−3

This radioactive element is known almost as well as uranium. It is also the heaviest (not densest)  primordial element, from before the Earth formed. It is most known for it's use in nuclear weapons, though now used in some long range spacecraft and older pacemakers.

A piece of plutonium about 3cm in diameter. image: adapted from wikipedia

Use, natural applications or common combinations: 

  • nuclear reactors
  • some used in spacecraft as a heat source
  • used in some pacemakers

Basic characteristics:

  • Standard atomic weight: (244)
  • Melting point: 639.4 °C
  • Boiling point:  3228 °C
  • Radioactivity: all radioactive
    • 244Pu with a half-life of  8.08 × 107 years emitting  alpha particles (this is what makes it warm)
    • 238Pu  with a half-life of 87.74 years also via alpha.