Uranium - for economical exploitation - exist in mines.
But uranium is is a common element in all rocks, all waters, building materials, soils etc.
Uranium-235 is found in nature at about 0.7% concentration to uranium-238.
In nature, uranium is found as uranium-238 (99.284%), uranium-235 (0.711%),[4] and a very small amount of uranium-234 (0.0058%)
Yes
Uranium is a metallic element and is not classified as an acid or a base. It is a radioactive element that can be found in nature as uranium-238 and uranium-235 isotopes.
I believe it is Uranium. All elements heavier than uranium are man-made. Here's an interesting article... http://space.newscientist.com/article/dn13828-has-the-heaviest-element-been-found.html
Radon (Rn)
Protactinium exist in minute traces in uranium ores.
Actinium is found in uranium and thorium ores.
Uranium is most commonly found in its natural state within various types of minerals, such as uraninite and pitchblende. These minerals are typically found in igneous rocks or sandstone deposits. Due to its radioactivity and chemical properties, uranium is rarely found in its pure form in nature.
For example uranium tetrachloride is not a natural product.
Actinium exist in minute traces in uranium and thorium ores.
Uranium is primarily found in the Earth's crust in the form of uranium oxides, such as uraninite. These minerals can exist as solid deposits in rocks or as part of sedimentary layers. Due to its radioactive nature, uranium undergoes decay processes that produce various daughter isotopes, contributing to its radioactivity.