The units of resistivity don't come out right.

10^-8 Ohm * m
or
m Ohm * cm

the 'm' should be a 'mu', but unfortunately they both look the same in the latin alphabet.

Polonium has no biological role and any sample used to kill the former KGB spy must have come from either a research laboratory or nuclear facility. It is found in uranium ores but at miniscule levels 0.00000001%. So small that the Curie's were awarded the Nobel prize for their superhuman effort to extract it. Could a terrorist smuggle Polonium into this country or is there a human leak at a UK Defence Establishment? Gramme quantities of polonium-210 are synthesized from bismuth in nuclear reactors. Carrying quantities of polonium is difficult because of the high temperature from radioactive decay [500oC] and the emission of deadly alpha particles. These radioactive particles are most dangerous when ingested. They pick up electrons from cells in the body and escape as helium gas. Polonium-210 has a relatively short half life [138 days] so the 'evidence' diminishes constantly with time. Also Polonium is fairly volatile and will evaporate if not kept in a sealed container. Polonium is one of the deadliest known substances and is believed to be a trillion more times toxic than HCN weight for weight.

It is suggested that poisoning by polonium-210 may have caused the death of Alexander Litvinenko, said to be a former Russian spy, in November 2006. Following his death at the end of November 2006, traces of polonium were found at several places he had visited before becoming ill. Before his death it was thought that thallium, or even radiothallium, might have been the cause of his illness. At the time of writing it is not clear who killed him, but not surprisingly the Russians deny it. Polonium-210 decays through the emission of α-particles and these emissions are noramlly easy to stop, but they are very dangerous if the polonium is inside the body.

Polonium is radioactive and present only in extremely low abundances in the environment. It is quite metallic in nature despite its location beneath oxygen in the periodic table. It is made in very small quantities through a nuclear reaction of bismuth. Neutron irradiation of ²⁰⁹bismuth (atomic number 83) gives ²¹⁰polonium (atomic number 84).

²⁰⁹Bi + ¹n → ²¹⁰Po + e^-

Polonium-210, ²¹⁰Po, transmutes into the lead isotope ²⁰⁶Pb by the emission of an α-particle. The half life for this process is just over 138 days meaning that after 138 days one-half of the original ²¹⁰Po has disappeared and after 2 times 138 days ³/₄ has gone.

²¹⁰₈₄Po → ²⁰⁶₈₂Pb + ⁴₂He

The short half life of polonium-210 and the heat generated with the above radioactive decay means that polonium metal generates considerable heat (141 W), meaning that the metal and its compounds self-heat. This is a useful property and polonium can be used as a small heat source (if expensive!). It can be used in space satellites for this purpose and is especially desirable as there are no moving parts. It was also used in the lunar rovers to keep internal parts warm during the frigid lunar nights.

Polonium metal is unique in that it is the only element whose structure (known as the α-form) is a simple cubic array of atoms in which each atom is surrounded by six other polonium atoms. On gentle warming to 36°C, this converts into a second form known as the β-form.