 Introduction to the Periodic Table In 1869, a Russian scientist named Dmitry Mendeleev made a chart of the known elements. The chart is called the Periodic Table of Elements. The Periodic Table shows elements arranged according to atomic number. Atomic number is the total number of protons in the nucleus. Each row across the table is called a period. There are seven periods. Each element in the period has the same number of electron shells. Each column in the table is called a group or family of elements. The two rows of elements shown below the original table were discovered after Mendeleev developed his original organizational table. This table shows you where they would fit in if we would add them to the original table. We don't add them to the table because they would shift the original organization Mendeleev created, putting the elements out of line. Therefore, they are not highlighted when showing the groups. Elements in the same group have similar physical and chemical properties. They also have the same number of electrons in their outermost shells. For example, group 1A elements are known as the alkali metals. They are soft, shiny metals that are good conductors of heat and electricity. They also have low melting points. All metals are on the left side of the table. Non-metals are on the right side of the table. A step-like line separates them. Each box in the table gives you important information about the element. The symbol for the element. The name of the element. The atomic number. The atomic weight. You have completed this learning object. Introduction to the periodic table.