Why is polonium so much more toxic than other radioactive elements?

Question

Why is polonium so much more toxic than other radioactive elements?

In: Chemistry

Answer 1

A major reason is that polonium is a lot more radioactive than things like uranium or even radium. When we say an element is radioactive, we mean that the atoms are unstable. These unstable atoms move toward a more stable state by shooting out a high-energy particle, shedding excess energy and turning into a different kind of atom (for instance polonium turns into lead). This process is called radioactive decay. The high-energy particles are what make radioactivity dangerous; they can knock electrons off of atoms and break the bonds that hold molecules together. The main concern for us is that this results in damage to the DNA in our cells.

Now, you may have heard of something called the half-life of a radioactive substance. This is the time it takes for half of the atoms of some radioactive substance to decay. That is, no matter how much of the substance you have now or how long it’s been around, half of the atoms will have decayed after one half-life.

Different isotopes have different half-lives. If the half-life is shorter, that means it decays faster, and emits more particles in the same amount of time. So effectively, the shorter the half-life, the more radioactive something is. Comparing half-lives now:

Uranium-238: 4.5 billion years

Radium-226: 1600 years

Polonium-210: 138 days (4.5 months)

This means that, for the same number of atoms, polonium-210 is about 4,200 times more radioactive than radium-226 and *12 billion* times more radioactive than uranium-238.

There are some things with shorter half-lives (such as the radon that occurs in basements) but generally they are in such tiny amounts that they don’t pose an immediate danger.