Atomic nonmetal

Components That Occupy the Lattice Points Metal atoms Nonmetal atoms Group 8A atoms Discrete molecules Ions... 

Metal ions are smaller than their neutral atoms. Nonmetal ions are larger than their neutral atoms. 

Consider a compound of magnesium and chlorine. To achieve a stable electron arrangement, a Mg atom (metal) loses its two valence electrons to form Mg ". Two Cl atoms (nonmetals) each gain one electron to form two Cl ions. The two CF ions are needed to... 

Complex carbides are very numerous. Many newer compounds of this class have been discovered and their stmctures elucidated (20). The octahedron M C is typical where the metals arrange around a central carbon atom. The octahedra may be coimected via corners, edges, or faces. Trigonal prismatic polyhedra also occur. Defining T as transition metal and M as metal or main group nonmetal, the complex carbides can be classified as (/)... 

Given the efficiency of VASP, electronic structure calculations with or without a static optimization of the atomic structure can now be performed on fast workstations for systems with a few hundred inequivalent atoms per cell (including transition-metais and first row elements). Molecular dynamics simulationsextending over several picoseconds are feasible (at tolerable computational effort) for systems with 1000 or more valence electrons. As an example we refer to the recent work on the metal/nonmetal transition in expanded fluid mercury[31]. 

Nonmetal atoms form negative ions (anions—pronounced AN-i-ons) by gaining electrons. Consider, for example, what happens when atoms of the nonmetals chlorine and oxygen acquire electrons ... 

When a nonmetal forms two oxoanions, the suffix -ate is used for the anion with the larger number of oxygen atoms. The suffix -ite is used for the anion containing fewer oxygen atoms. 

When a nonmetal forms more than two oxoanions, the prefixes per- (largest number of oxygen atoms) and hypo- (fewest oxygen atoms) are used as well... 

As pointed out in Chapter 2, elements close to a noble gas in the periodic table form ions that have the same number of electrons as the noble-gas atom. This means that these ions have noble-gas electron configurations. Thus the three elements preceding neon (N, O, and F) and the three elements following neon (Na, Mg, and Al) all form ions with the neon configuration, is22s22p6. The three nonmetal atoms achieve this structure by gaining electrons to form anions ... 

The differences in radii between atoms and ions can be explained quite simply. A cation is smaller than the corresponding metal atom because the excess of protons in the ion draws the outer electrons in closer to the nucleus. In contrast, an extra electron in an anion adds to the repulsion between outer electrons, making a negative ion larger than the corresponding nonmetal atom. 

Earlier we referred to the forces that hold nonmetal atoms to one another, covalent bonds. These bonds consist of an electron pair shared between two atoms. To represent the covalent bond in the H2 molecule, two structures can be written ... 

This idea is readily extended to simple molecules of compounds formed by nonmetal atoms. An example is the HF molecule. You will recall that a fluorine atom has the electron configuration ls22s22p5. ft has seven electrons in its outermost principal energy level (n = 2). These are referred to as valence electrons, in contrast to the core electrons filling the principal level, n = 1. If the valence electrons are shown as dots around the symbol of the element, the fluorine atom can be represented as... 

These examples illustrate the principle that atoms in covalently bonded species tend to have noble-gas electronic structures. This generalization is often referred to as the octet rule. Nonmetals, except for hydrogen, achieve a noble-gas structure by sharing in an octet of electrons (eight). Hydrogen atoms, in molecules or polyatomic ions, are surrounded by a duet of electrons (two). 

In molecules of this type, the terminal atoms are most often halogens (F, Cl, Br, I) in a few molecules, oxygen is a terminal atom. The central atom is a nonmetal in the third,... 

In the past 40 years, compounds have been isolated in which xenon is bonded to several nonmetals (N, C, and Cl) in addition to fluorine and oxygen. In the year 2000, it was reported [Science, Volume 290. page 117) that a compound had been isolated in which a metal atom was bonded to xenon. This compound is a dark red solid stable at temperatures below -40°C it is believed to contain the [AuXe4F+ cation. 

The small size of the hydrogen atom allows the unshared pair of an F, O, or N atom of one molecule to approach the H atom in another very closely. It is significant that hydrogen bonding occurs only with these three nonmetals, all of which have small atomic radii. 

Diagrams of four types of substances (see text discussion). X represents a nonmetal atom, — represents a covalent bond, M+ a cation, X- an anion, and e an electron. 

The transition metals, unlike those in Groups 1 and 2, typically show several different oxidation numbers in their compounds. This tends to make their redox chemistry more complex (and more colorful). Only in the lower oxidation states (+1, +2, +3) are the transition metals present as cations (e.g., Ag+, Zn2+, Fe3+). In higher oxidation states (+4 to +7) a transition metal is covalently bonded to a nonmetal atom, most often oxygen. 

Strategy Referring to Table 21.3, find an oxide in which the central nonmetal atom has the same oxidation number as in the acid. 

Table 21.4 lists some of the more important oxoacids of the nonmetals. In all these compounds, the ionizable hydrogen atoms are bonded to oxygen, not to the central nonmetal atom. Dissociation of one or more protons from the oxoacid gives the corresponding oxoan-ion (Figure 21.8, p. 567). 

Trends in acid strength can be explained in terms of molecular structure. In an oxoacid molecule, the hydrogen atom that dissociates is bonded to oxygen, which in turn is bonded to a nonmetal atom, X. The ionization in water of an oxoacid H—O—X can be represented as... 

Strategy The structure can be obtained by removing an oxygen atom from H O, (Figure 21.8). Relative acid strengths can be predicted on the basis of the electronegativity and oxidation number of the central nonmetal atom, following the rules cited above. 

Carbon atoms may be bonded to each other or to other nonmetal atoms, most often hydrogen, a halogen, oxygen, or nitrogen. In most organic compounds—... 

Chemical reaction A process in which one or more substances, called reactants, are converted to product(s), 67. See also Reaction, nonmetals, 575q, 555-558 Chernobyl nuclear accident, 525-526 Chiral center Carbon atom bonded to four different groups, 600 Chiral drugs, 601 Chloride ores, 535-536 Chlorinated water, 556 Chlorine... 

Formula An expression used to describe the relative numbers of atoms of different elements present in a substance, 34 mass relations in, 69-70q nonmetals, 575q... 

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