[CCKitty (OP)]

Greetings all.  I am not a chemist, but I have taken college level chemistry courses.  I watched a science special called "Uranium".  It was so interesting - I recommend it. 

My brain lets me follow the pathway of Uranium's transition through the 14 steps to lead, but I  glitch at the "radon to polonium"  level.  Is anyone here able to help a lay-person (with a bit of chemistry knowledge)  understand this step?  Would the radon gas turn to a polonium precipitate? 

How does radon (a gas) become solid polonium?

Thanks in advance.

[Origin]

Radon gas alpha decays to Polonium particulate.

[Bored chemist]

The radon decays to a single atom of polonium and that usually sticks to a grain of dust.

[alancalverd]

Radon would only appear in gaseous form at the surface or in a solution of uranium. The decay series within the bulk of the metal leads to all the intermediates and stable lead being present as individual atoms dispersed through the matrix, from which the metals can be extracted by sequential crystallisation of their salts. 

[evan_au]

It all has to do with the column in the periodic table.
- The right-hand column is called "noble gases" because they have a full outer shell of electrons, their outer orbital shape is very symmetrical, and so they don't have a strong electric or magnetic field that attracts them to other atoms - so they are very chemically non-reactive, and remain as gases.
- Radon (element 86)  is a noble gas, with a boiling point of -61C. So virtually anywhere on Earth (except maybe midwinter at the South Pole), Radon will be a gas.
- Radium decays into Radon. Radium (element 88) is in the second column, so it is fairly reactive (like Calcium), so it will chemically react with many things. It's melting point is 960C, so most places on the surface of the Earth it will be a solid (except in very hot lava).
- Radon decays into Polonium (element 84). Polonium is in the 6th column, the same as oxygen and sulphur, so it is moderately reactive. The melting point is 254C, so it will be a solid at room temperature.
- Note that these melting & boiling points are measured with the pure element, which is unlikely to be found in nature. But they are indicative of the element's volatility.

Radon gas turning into solid Polonium is no more surprising than solid Radium turning into Radon gas. Indeed, this transmutation was thought by chemists to be impossible.
- Alchemists had tried for centuries to make gold - and failed. Their confusion was clarified with the invention of the periodic table, which were finally thought to be fundamental atoms that were immutable (unlike their compounds).
- Soddy (a chemist) was stunned when he discovered the transmutation of Radium into Radon in Rutherford's lab. He received a Nobel Prize for his work.
https://en.wikipedia.org/wiki/Frederick_Soddy

Most importantly for your health, if you breathe in Radon gas, and it decays while in your lung, your delicate living lung tissue gets hit by 1 alpha particle from the Radon gas, then a series of additional insults from positrons and alpha particles as the solid Polonium decays further.
- So its a good idea to keep your basement well ventilated if you live in a high-radon environment (eg built on granite rock).