I don't understand, according to the periodic table at web elements;

Question

An isotope of Element 116 (292Uuh) was identified in the reaction of 248Cm with 48Ca. It is very shortlived and decomposes to a known isotope of element 114, 288114Uuq.

How can it be that ununhexium is shortlived and decomposes, my OU books harp on about atoms not being able to decompose, atoms always stay the same but are merely attracted to different atoms.

Does anybody catch my drift.

While were on the subject of ununhexium, how do we know it exists if weve not even found it yet, let alone give it a specific place in the table? Do they want to have a guess at what aliens look like and what kind of houses they live in while they're at it?

For starters, it is good to be skeptical and it is good to inject some humor along with being skeptical, but let's not make things harder than they are. Do I detect a slight chip on the shoulder? Your question is a good one.

You are correct about atoms not being able to decompose (in some senses) and always stay the same but attract different atoms. BUT the decomposition we are talking about with Uuh is the decomposition of the nucleus; i.e., radioactivity. I know you have heard about radioactivity. Nuclei of many many elements decompose giving off alpha and or beta particles as well as gamma rays. So while most atoms do stay the same, the nuclei of many decompose to more stable arrangements. And the "while we're on it bit," your post said it had been discovered by bombarding 238Cm and 48 Ca (or is that 40 Ca?) so it must have been discovered. As to where it's placed, if it has an atomic mass of 116, then it must follow 115 and precede 117 (although they have not yet been discovered yet.) One thing that is nice about the periodic table is that we can often predict the properties of elements even before they have been discovered. In fact, that is why Mendeleev's arrangment in one of the first periodic tables back in the early days was so successful. He successfully predicted that eka-silicon (now named germanium), unknown at the time, would be discovered one day and it would have such and such properties. It was discovered about 16 years later and the properties were very close to the predictiions of Mendeleev. I hope this helps clear up any confusion about stability of atoms and where they are placed in the periodic table.