Periodic table observed that carbon often has four other atoms bonded to it. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventually became known as valency; different elements bond with different numbers of atoms. In 1862, Alexandre-Emile Béguyer de Chancourtois, a French geologist, published an early form of periodic table, which he called the telluric helix or screw. He was the first person to notice the periodicity of the elements. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois showed that elements with similar properties seemed to occur
Periodic table the island of stability, which is expected to centre around element 126, as the extension of the periodic and nuclides tables is restricted by proton and neutron drip lines. Other predictions of an end to the periodic table include at element 128 by John Emsley, at element 137 by Richard Feynman, and at element 155 by Albert Khazan. The Bohr model exhibits difficulty for atoms with atomic number greater than 137, as any element with an atomic number greater than 137 would require 1s electrons to be travelling faster than "c", the speed of light. Hence the non-relativistic Bohr model