Why does an alpha particle have 40mm range in air?

[Dixanadu]

Hey everyone...

so I understand that an alpha particle, being a helium nucleus, is quite a large particle compared to, for example, a beta particle. Due to this, it will encounter a lot more collisions and impart its momentum to other particles of air at a much more rapid rate.

Is there anything I'm missing here at a simple level? perhaps any equations that this is due to?

 

[davenn]

very simply ...

the alpha particle will easily take a couple of stray electrons and become a stable Helium atom and thereby ceasing to exist as a radiating particleDave

 

[Lok]

First a wiki:
https://en.wikipedia.org/wiki/Alpha_particle#Energy_and_absorption

From there to note that, the alpha particles are slow in comparison to beta and neutrons speeds. Also the charge is double. And only by these two you would get a lot more interaction with other charged particles on it's path.