Periodic table of elements

                                                                                      The Periodic Table of Elements (or Mendeleev's Table) was designed in 1869 by Russian chemist Dmitry Ivanovich Mendeleev. The periodic table classifies all chemical elements according to their atomic number and chemical properties.

                                                                                      Definition of a chemical element

                                                                                      Set of atoms characterized by a defined number of protons in their nucleus. These atoms have different possible forms: isotopes (same number of protons and electrons but different number of neutrons).

                                                                                      Atomic number : number of protons and electrons of the element

                                                                                      Atomic symbol : universal representation of the element

                                                                                      Mendeleeev

                                                                                      Dmitry Ivanovich Mendeleev (or Dmitry Mendeleev) designed the periodic table in 1869. He is a Russian chemist. He was born on February 8, 1834 in Tobolsk (Siberia, Russia). He died on February 2, 1907 in Saint Petersburg.