According to this site, they have succeeded in making an element with atomic number 118 by shooting a stream of krypton atoms at a lead target. The element 118 then immediately emitted an alpha particle and decayed into 116, then again into 114, and so on down to 106.
I have two questions about this. First, how do they know that they got element 118 to begin with? If it only lasted a millisecond before decaying, how can they measure the properties of the result?
Second, how do they know what it decayed into? I’m assuming the alpha particle had some measurable energy level as it shot off, but how is that caught?
I’ve got a classroom full of twelve year olds dying for the answer to this question. Thanks in advance for any help.
If you read carefully, you will see that this work has been retracted, and 118 has not been made.
If they had made it, they would identify it by its charge-to-mass ratio, which can be calculated from its trajectory through a magnetic field, and its characteristic decay pattern, which can also be determined from trajectories. This sort of thing used to be done with cloud chambers, but it’s all electronic detectors now, and I don’t know much about them.
Here is a good comprehensive source on discovering heavy elements. Basically, it is the decay products themselves that are examined for the observation to be made. We think we have a pretty good understanding of how particles decay, what forces they experience, and what we expect from the conditions of the laboratory. Knowing this, we can analyze the detections of various decay products (usually done by looking for their interactions with detectors… whether those interactions be collisions or excitations or energy exchanges) and essentially “work backwards” to figure out what we did. This is how the heaviest elements have been found.