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This is polonium.

Symbol Po
Atomic number 84
Atomic mass (209) amu

Polonium was discovered in 1898, in samples of uranium-bearing pitchblende. But the sample was far more radioactive than the uranium should make it. It was suspected that at least one additional radioactive substance was in the mixture. Several tons of the pitchblende was refined and, an ounce at a time, two new elements that were highly radioactive were isolated:

  • polonium, and
  • radium

Distinguishing properties

Polonium is an extremely rare, naturally radioactive element. Polonium-210 is the only isotope produced commercially. It is shown in the image as a thin film on a stainless steel disc, the form in which it is sold as an alpha-particle source for scientific use.


Polonium is used as a neutron source in nuclear reactors and as an alpha-particle generator. Like other radioactive elements, polonium is a hazardous toxic agent and should be handled with proper protective equipment.

See also

Periodic table of the elements