The Periodic Table
The periodic table organizes and displays the different elements found in nature. Devised by Russian chemist Dmitri Mendeleev (1834–1907) in 1869, the table groups elements that, because of some commonalities of their atomic structure, share certain chemical properties. The atomic structure of elements is responsible for their physical properties including whether they exist as gases, solids, or liquids under specific conditions and their chemical reactivity, a term that refers to their ability to combine and to bond chemically with each other and other elements.
In the periodic table, shown below, the elements are organized and displayed according to their atomic number and are arranged in a series of rows and columns based on shared chemical and physical properties. Besides providing the atomic number for each element, the periodic table also displays the element’s atomic mass. Looking at carbon, for example, its symbol (C) and name appear, and its atomic number of six (in the upper right-hand corner showing the number of protons in the neutral nucleus) and its atomic mass of 12.11 (sum of the mass of electrons, protons, and neutrons).