Nonmetals bonding

VIA nonmetals) very easily gain new valence electrons. So metals and nonmetals tend to form bonds in which the metal atoms entirely surrender valence electrons to the nonmetals. Bonds with extremely unequal electron-sharing are called ionic bonds. 

Dichlorine is CI2, a compound formed when one chlorine atom bonds to another. Because each atom in the compound is of the same element, the two atoms have the Scime electronegativity. The difference in electronegativity between the two atoms is zero, so the bond between the two chlorine atoms must be covalent. Another easy way to tell that the bond is covalent is to recognize that chlorine is a nonmetal and is bonded to itself and that two nonmetals bonded together usually form a covalent bond. The electron dot structure of dichlorine is in the following figure ... 

Although typical organic molecules, such as those of which all living things are composed, are constructed from only a few elements (usually C, H, O, N, S, and P and, on occasion, Cl, Br, I, and a few more), there are very many other elements that can be used as the basis for reagents, catalysts, and as components of synthetic intermediates. The metals will be discussed in the next chapter (48) but many main group (p block) elements are also important. These nonmetals bond covalently to carbon and some of their compounds are important in their own right. 

To write electron dot diagrams for the compounds of two or more nonmetals bonded with shared electron pairs, and also for polyatomic ions... 

You already know how to name monatomic ions. How do you name polyatomic ions Most polyatomic ions are oxyanions. An oxyanlon is a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms. Many oxyanions contain the same nonmetal and have the same charges but differ in the number of oxygen atoms. More than one oxyanion exists for some nonmetals, such as nitrogen and sulfur. These ions are easily named using the following conventions. 

Nearly all binary molecular compormds involve two nonmetals bonded together. Although many nonmetals can exhibit different oxidation numbers, their oxidation numbers are not properly indicated by Roman numerals or suffixes. Instead, elemental proportions in binary covalent compounds are indicated by using a prefix system for both elements. The Greek and Latin prefixes for one through ten are mono, di, tri, tetra, penta, hexa, hepta, octa, nona, and deca. The prefix mono- is omitted for both elements except in the common name for CO, carbon monoxide. We use the minimum number of prefixes needed to name a compound unambiguously. The final a in a prefix is omitted when the nonmetal stem begins with the letter o we write heptoxide, not heptaoxide. ... 

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. 

Atoms (usually nonmetals) bonded by shared e pairs... 

Always eager to push limits, chemists have devoted considerable attention to constructing Xe-nonmetal bonds involving elements less electronegative than F or O. For Xe-N bonds, interaction of the rather acidic bis(fluorosulfonyl)imide and XeF2 does the trick ... 

Two types of acids are named differently. Water solutions of binary covalent compounds containing hydrogen and a nonmetal are named following the pattern hydro(stem)ic acid, where (stem) is the stem of the name of the nonmetal bonded to hydrogen. Acids in which hydrogen is bonded to polyatomic ions have names based on the name of the polyatomic ion to which hydrogen is bonded. 

Recall from Chapter 5 that when nonmetals bond with other nonmetals, a molecular compoimd results. Molecular compounds contain covalent bonds in which electrons are shared between atoms rather than transferred. In Lewis theory, we represent covalent bonding by allowing neighboring atoms to share some of their valence electrons in order to attain octets (or duets for hydrogen). For example, hydrogen and oxygen have the Lewis structures ... 

The Problem with Assuming Complete Dissociation Before we focus on calculations, let s address a complication that affects accuracy, resulting in approximate answers. We ve been assuming that the small amount of slightly soluble ionic compounds that does dissolve dissociates completely into separate ions, but this is an oversimplification. Many slightly soluble salts have polar covalent metal-nonmetal bonds (Section 9.5), and partially dissociated or even undissociated species occur in solution. Here are two of many examples ... 

Chemical compounds are divided into two types, ionic and molecular, each with its own naming system (4.3, 4.4). An ionic compound is a metal bonded to a nonmetal via an ionic bond. In an ionic bond, an electron is transferred from the metal to the non-metal, making the metal a cation (positively charged) and the nonmetal an anion (negatively charged). In its solid form, an ionic compound consists of a three-dimensional lattice of alternating positive and negative ions. A molecular compound is a nonmetal bonded to a nonmetal via a covalent bond. In a covalent bond, electrons are shared between the two atoms. Molecular compounds contain identifiable clusters of atoms called molecules. 

In general, atoms of metals bond ionically with atoms of non-metals, atoms of metals bond metallically with each other, and atoms of nonmetals bond covalently with each other. 

Such a behaviour of the electron density distribution agrees well with the results of X-ray diffraction measurements (Kubel, Flack and Ivon, 1987) and can be explained qualitatively making use of the covalency parameters and the densities of f2g and states. In TiC and other carbides there are eight electrons per unit cell, and the electron density symmetry is determined mainly by C2p electrons and the admixture of metal d states, which have mainly the symmetry component. As the number of valence electrons in carbides increases, the contributions of the t2g metal states also increase. Such an effect takes place when going from carbides to nitrides. However, in all cases there are no local maxima in the electron density distribution in the metal-nonmetal direction, which would be expected taking into account covalency. Inside nonmetal atomic spheres the distribution of the valence electrons is close to spherical, and the presence of the covalent metal-nonmetal bonds is revealed in the deformation of electron density in the direction away from the centres of metalloid atoms to the metal atoms, see Fig. 3.4. 

---