Alpha Particles and Helium

[Mohit Pandey]

Radioactive substances emit Alpha Particles which are He2+ ion or the helium nucleus. Then all these substances such as radium and uranium contain some amount of helium. Am I correct? :eek_big:

[Mercedes Benzene]

Radioactive substances emit Alpha Particles which are He2+ ion or the helium nucleus. Then all these substances such as radium and uranium contain some amount of helium. Am I correct? :eek_big:

Not really. I mean, I guess you could think of it that way, but the Helium does not exist as Helium in the radioactive substance. An alpha particle is just two protons and two neutrons bound together, and those are ejected from the nucleus of the radium or uranium or what have you. It's only effective as Helium once it leaves the nucleus of the other substance.

[CraigD]

Mercedes states it nicely, I think. I’d add only one, I hope, helpful detail: not all radioactive decay is alpha decay, where a 4He nucleus is released. Not even all commonly observed decay events are. In particular, events when the decay product’s atomic number is only 1 less than its parent (eg: 207Tl to 207 Pb) are beta decay, where the massive by-product is an electron, (a beta- particle).

 

This is pretty well described at many reference websites, including the wikipedia articles “radioactive decay/modes of decay” and ”decay chain”.