Uranium has the highest atomic weight of the primordially occurring elements.
Its density is about 70% higher than that of lead, and slightly lower than that of gold or tungsten.
The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay.
The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.
Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers.
So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value.
So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive.
In air it is coated by uranium oxide, tarnishing rapidly. Uranium can form solids solutions and intermetallic compounds with many of the metals.
Depleted uranium is used as shelding to protect tanks, and also in bullets and missiles.