Compound of metals with nonmetals

Compounds of metals with nonmetals are nsnally ionic. Nonmetal-norunetal compounds are usually molecular. 

Most binary compounds (compounds of two elements) of metals with nonmetals are essentially ionic. All compounds involving only nonmetals are essentially covalent except for compounds containing the NH4+ ion. We do not consider compounds of metals with metals in this course. 

I ILICON-CONTAINING CERAMICS include the oxide materials, silica and silicates the binary compounds of silicon with nonmetals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides and, finally, elemental silicon itself. Throughout the world, research activity on the preparation of all of these classes of solid silicon compounds by newer preparative techniques is vigorous. 

Let us describe some combinations of metals with nonmetals to form ionic compounds. 

In the previous section, the ionic bond and the reaction of metals with nonmetals to form ionic compounds were discussed. In this section, we examine the nature of the bond between atoms of two nonmetals, those elements to the right of the stair step on the periodic table. You will recall that in reactions between metals and nonmetals, metals lose electrons to form cations and nonmetals acquire them to from anions. But what if both elements are nonmetals Nonmetals, like O, Br, or N, do not lose electrons easily if anything, they prefer to acquire them. As a result, when two nonmetals bond to one another, they do so by sharing electrons forming bonds described as covalent. A covalent bond is a pair of electrons shared by two atoms. Compounds that are held together by covalent bonds are called covalent compounds, and they exist as individual molecules. Covalent bonding provides a second way for atoms to acquire an octet of electrons in their valence shells. The pair of electrons shared by two atoms becomes part of the valence shell of both atoms. 

It should be noted that the mentioned molybdenum disilicide is a borderline case of the intermetallics since silicon is not a metal, but a semiconductor. It is known that the combination of silicon with metals gives rise to compounds with metallic properties, e.g. MoSij, as well as compounds with semiconductor properties (Nowotny, 1963), i.e., silicides mark the transition from intermetallics to compounds of metals and nonmetals. Nevertheless, silicides are traditionally included in the field of intermetallics because of their many similarities with metals (Wehrmann, 1967). 

Some of the properties of substances can be discussed in a useful way in terms of the sizes of ions or atoms. Many of the substances mentioned in the later sections of this chapter and in the following chapter are compounds of metals, with small electronegativity, and nonmetals, with large electronegativity. The bonds between these atoms may have a sufficiently large amount of ionic character to justify the discussion of the substance as composed of cations and anions. Such a discussion may be helpful even for substances in which the bonds have a large amount of covalent character. 

Berzehus (19) further appHed and amplified the nomenclature introduced by Guyton de Morveau and Lavoisier. It was he who divided the elements into metalloids (nonmetals) and metals according to their electrochemical character, and the compounds of oxygen with positive elements (metals) into suboxides, oxides, and peroxides. His division of the acids according to degree of oxidation has been Httie altered. He introduced the terms anhydride and amphoteric and designated the chlorides in a manner similar to that used for the oxides. 

Selenides. Selenium forms compounds with most elements. Biaary compounds of selenium with 58 metals and 8 nonmetals, and alloys with three other elements have been described (55). Most of the selenides can be prepared by a direct reaction. This reaction varies from very vigorous with alkah metals to sluggish and requiring high temperature with hydrogen. 

Lithium hydride is a strong reducing agent and would, therefore, react with compounds that contain oxygen. Even many highly stable oxides of metals and nonmetals can be reduced. It reduces metal oxides to metals and carbon dioxide to carbon ... 

To write octet rule electronic structures for the formation of ionic compounds and to deduce the formulas of compounds of main group metals with nonmetals... 

The solid crust and the upper mantle make up the region called the lithosphere. Oxygen is the most abundant element in the lithosphere. Unlike the hydrosphere and the atmosphere, the lithosphere contains a large variety of other elements, including deposits of alkali, alkahne earth, and transition metal elements. Table 26-3 lists the most abundant elements in the continental crust portion of the hthosphere. With the exception of gold, platinum, and a few other rare metals that are found free in nature, most metallic elements occur as compounds in minerals. A mineral is a solid, inorganic compound found in nature. Minerals have distinct crystalhne structures and chemical compositions. Most are combinations of metals and nonmetals. 

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