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[8] [9] There is no widely accepted precise definition; [10] any list of nonmetals is open to debate and revision. [1] The elements included depend on the properties regarded as most representative of nonmetallic or metallic character. Fourteen elements are almost always recognized as nonmetals: [1] [2]
Some textbooks use the term nonmetallic elements such as the Chemistry of the Non-Metals by Ralf Steudel, [25]: 4 which also uses the general definition in terms of conduction and the Fermi level. [ 25 ] : 154 The approach based upon the elements is often used in teaching to help students understand the periodic table of elements, [ 26 ...
This gradual reduction in the number of nearest neighbours corresponds (approximately) to a reduction in metallic character. A similar progression is seem among the metals. Metallic bonding tends to involve close-packed centrosymmetric structures with a high number of nearest neighbours.
The most stable form is the black allotrope, which is a metallic looking, brittle and relatively non-reactive semiconductor (unlike the white allotrope, which has a white or yellowish appearance, is pliable, highly reactive and a semiconductor). When assessing periodicity in the physical properties of the elements it needs to be borne in mind ...
Silicon is a metallic-looking relatively unreactive solid with a density of 2.3290 g/cm 3, and is hard (MH 6.5) and brittle. It melts at 1414 °C (cf. steel ~1370 °C) and boils at 3265 °C. Silicon has a diamond cubic structure (CN 4). It is a non-conductive with a band gap of about 1.11 eV. [3]
Metallic character increases going down a group and from right to left across a period. Nonmetallic character increases going from the bottom left of the periodic table to the top right. The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869; he formulated the periodic law as a dependence ...
Across each period, from left to right, the increasing attraction between the nuclei and the outermost electrons causes the metallic character to decrease. In contrast, the nonmetallic character decreases down the groups and increases across the periods. [27] [28]
Nitrogen and bismuth, despite both being pnictogens, are very different in their physical properties. For instance, at STP nitrogen is a transparent non-metallic gas, while bismuth is a silvery-white metal. [12] The densities of the pnictogens increase towards the heavier pnictogens. Nitrogen's density is 0.001251 g/cm 3 at STP. [12]