Block (periodic table) the s-block, with its outer (and only) electrons in the 1s atomic orbital, although its chemical properties are more similar to the p-block noble gases due to its full shell. In addition to the blocks listed in this table, there is a hypothetical g-block which is not pictured here. The g-block elements can be seen in the expanded extended periodic table. Lanthanum and actinium are placed under scandium and yttrium to reflect their status as d-block elements, as they have no electrons in the 4f and 5f orbitals, respectively, while lutetium and lawrencium do. The s-block is on the left
History of the periodic table the Periodic Law for the chemical elements". He contributed the word 'periodic' in chemistry. The Russian chemist Dmitri Mendeleev was the first scientist to make a periodic table similar to the one used today. Mendeleev arranged the elements by atomic mass, corresponding to relative molar mass. It is sometimes said that he played 'chemical solitaire' on long train journeys, using cards with various facts about the known elements. On March 6, 1869, Mendeleev gave a formal presentation, "The Dependence Between the Properties of the Atomic Weights of the Elements", to the Russian Chemical Society. In 1869, the table was published