Thorium, at atomic number 90, is one of the rarest elements. In the universe, thorium is among the rarest of the primordial elements, because it is one of the two elements that can be produced only in the r-process (the other being uranium), and also because it has slowly been decaying away from the moment it formed.What element has the atomic number of 90?
Thorium is a weakly radioactive metallic chemical element with symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point.Where to find the atomic number?
In order to find the atomic number of any element, students can use a periodic table and look at the upper left-hand corner of a specific element. The atomic number is also the number of protons found in the nucleus of an element.