Is uranium a unique structure

Answer 1

Uranium is a metal, and, at atomic number 92, it's the heaviest of the elements produced by stars in fusion. Note that it's not made in "regular" stellar nucleosynthesis, but is created in the spectacular supernovae events of certain stars when they reach the end of their lives. In that light, that makes uranium like all the other elements heavier than iron. Uranium is also very dense, and it is nearly 20 times heavier than the same volume of water. There's more. Uranium is radioactive.

All the isotopes of uranium have unstable nuclear configurations. These nuclei will decay over time, all of them, and they all transform by spontaneous fission or by alpha decay. The three isotopes that make up natural uranium, 234U, 235U and 238U, have long half-lives. The 234U has a half million year half-life, and the half-lives of the other two are on the order of a billion years. There's one other thing, and that's that 235U is fissile.

It turns out that 235U is capable of creating a nuclear chain reaction when critical mass is reached because it fissions when undergoing neutron capture. All uranium is going to be decaying over time, but when the critical mass of 235U is reached, a chain reaction will begin where neutrons spontaneously released from some 235U atoms will cause other atoms to fission and release neutrons. The chain will begin, and only the physics and geometry associated with the critial mass will determine how far the chain will build and how long it will progress. The translation of that is that if use conventional explosives to drive subcritical masses of 235U together, we can, if things are optimized, create a nuclear explosion. We can also design "surrounds" that will cause a chain reaction to begin and will also promote the chain to be continuous, as in a nuclear reactor.

Note that a trace of plutonium can be found in naturally occurring uranium ores, but uranium is generally thought of as being the heaviest naturally occurring nucleus. Let's not split hairs here. Oh, and if you need more information on uranium, use the link below. It will take you to the Wikipedia post, and it's a good read. You will be measureably smarter having gone through their article. But be warned that it may very well provide one or more questions for each answer it supplies - just like most good science.

Answer 2

Uranium is an element, just as oxygen, carbon, and iron. It has a unique crystaline structure like all metals.

Answer 3

Uranium is a natural chemical element, radioactive and the isotope 235U is fissionable with thermal neutrons releasing a great quantity of energy.

Answer 4

Because by nuclear fission of uranium an immense quantity of energy is released.