The Periodic Table is arranged so that nonmetals are on the right side of the chart and metals are on the center and to the left.  A metal, in chemical terms, is looking for valence electrons for its shell, while a nonmetal has valence electrons to donate. The color coding on the table helps determine this classification. Note the right-descending "staircase line" separating nonmetal and metals on the recommended Periodic Table of the Elements. The elements to the immediate left of the "staircase line" are called "semi-metals" or "metalloids" because they can behave chemically as either metals or nonmetals.

Martin E. Klaproth in 1782 discovered element 92 (Uranium) by extracting it from the mineral uraninite (UO₂).  He named the new element after Uranus, which had been discovered a few years earlier.   However all the properties of uranium were not discovered until Antoine Becquerel in 1896 discovered the mysterious properties of radioactivity.   There are 22 elements that are radioactive.     Uranium is important on the Periodic Table because it divides the natural elements found on Earth with elements that are synthetically derived.  Synthetic elements can only be created through nuclear fusion experimentation with nuclear reactors or particle accelerators. There are two exceptions including Technetium (Tc, 43) and Promethium (Pm, 61) which can be created synthetically for a short time.  However you can find trace amounts of the two elements in nature.