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Periodic table extract showing the nonmetallic elements. H is normally placed over Li in Group 1. It is shown here over F for comparative purposes. The asterisks show further alternative positions for H. The elements shown as metalloids are those commonly recognized as such by authors who include such a class.
In 1891, Walker published a periodic "tabulation" with a diagonal straight line drawn between the metals and the nonmetals. [14] In 1906, Alexander Smith published a periodic table with a zigzag line separating the nonmetals from the rest of elements, in his highly influential [15] textbook Introduction to General Inorganic Chemistry. [16]
Hydrogen is again placed by itself on account of its uniqueness. The remaining nonmetals are divided into metalloids, nonmetals, (referred to as "quintessential nonmetals"), halogens, and noble gases. Since the metalloids abut the post-transition or "poor" metals, they might be renamed as "poor non-metals". [11]
From left to right in the periodic table, the nonmetals can be divided into the reactive nonmetals and the noble gases. The reactive nonmetals near the metalloids show some incipient metallic character, such as the metallic appearance of graphite, black phosphorus, selenium and iodine. The noble gases are almost completely inert.
Periodic table of the chemical elements showing the most or more commonly named sets of elements (in periodic tables), and a traditional dividing line between metals and nonmetals. The f-block actually fits between groups 2 and 3 ; it is usually shown at the foot of the table to save horizontal space.
The term is sometimes also used when describing dopants of specific elements types in compounds, alloys or combinations of materials, using the periodic table classification. For instance metalloids are often used in high-temperature alloys, [29] and nonmetals in precipitation hardening in steels and other alloys. [30]
For example, the periodic table in the Encyclopaedia Britannica recognizes noble gases, halogens, and other nonmetals, and splits the elements commonly recognized as metalloids between "other metals" and "other nonmetals". [103] On the other hand, seven of twelve color categories on the Royal Society of Chemistry periodic table include nonmetals.
These sets usually do not aim to cover the whole periodic table (as for example period does), and often overlap or have boundaries that differ between authors. Some examples: Metals and nonmetals; Metalloids – Variously-defined group of elements with properties intermediate between metals and nonmetals. In alphabetic order: