The periodic table, also called the periodic table of elements, is an organized arrangement of the 118 known chemical elements. The chemical elements are arranged from left to right and top to bottom ...

Heavier main-group elements have fundamentally different electronic properties from their lighter congeners. Until the last two decades of the twentieth century, these differences were often masked by ...

Hafnium is a lustrous, silvery-gray transition metal. Discovered in 1923, it was the next-to-last element with stable nuclei to be added to the periodic table (the final one was rhenium in 1925).