Each one had a regular stepped line separating metals from nonmetals. Deming, an American chemist, published short ( Mendeleev style) and medium ( 18-column) form periodic tables. In 1906, Alexander Smith published a periodic table with a zigzag line separating the nonmetals from the rest of elements, in his highly influential textbook Introduction to General Inorganic Chemistry. In 1891, Walker published a periodic 'tabulation' with a diagonal straight line drawn between the metals and the nonmetals. References to a dividing line between metals and nonmetals appear in the literature as far back as at least 1869. The former generally combine with electropositive metals to make intermetallic compounds whereas the latter usually form salt-like compounds. It differentiates group 13 elements from those in and to the right of group 14. This particular line was named by Laves in 1941. While it has also been called the Zintl border or the Zintl line these terms instead refer to a vertical line sometimes drawn between groups 13 and 14. This line has been called the amphoteric line, the metal-nonmetal line, the metalloid line, the semimetal line, or the staircase. When presented as a regular stair-step, elements with the highest critical temperature for their groups (Li, Be, Al, Ge, Sb, Po) lie just below the line. Elements to the lower left of the line generally display increasing metallic behaviour elements to the upper right display increasing nonmetallic behaviour. The dividing line between metals and nonmetals can be found, in varying configurations, on some representations of the periodic table of the elements (see mini-example, right).
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