Group numbers, atoms

The number of valence elec trons in an atom of a main group element such as nitrogen is equal to its group number In the case of nitro gen this is five... 

When it is required to indicate the number of entire groups of atoms, the multiplicative numerals bis-, tris-, tetrakis-, pentakis-, and so on, are used (i.e., -kis is added starting from tetra-). The entity to which they refer is placed in parentheses. 

Other Polyatomic Anions. Names for other polyatomic anions consist of the root name of the central atom with the ending -ate and followed by the valence of the central atom expressed by its oxidation number. Atoms and groups attached to the central atom are treated as ligands in a complex. 

Nj = number of C-H atomic groups / bonded to at least one functional group or atom in tbe molecule of interest ny= number of different functional groups or atoms in tbe molecule of interest... 

Nj = number of functional groups or atoms A. in tbe molecule of interest... 

Some of the analytical methods utilize highly selective and sensitive detection techniques for specific functional groups of atoms in compounds, whereas others respond in a more universal manner, i.e., to the number of carbon atoms present in the organic molecule.- ... 

Figure C.6 shows another pattern in the charges of monatomic cations. For elements in Croups 1 and 2, for instance, the charge of the ion is equal to the group number. Thus, cesium in Group 1 forms Cs+ ions barium in Group 2 forms Ba2+ ions. Figure C.6 also shows that atoms of the d-hlock elements and some of the heavier metals of Groups 13/111 and 14/IV can form cations with different charges. An iron atom, for instance, can lose two electrons to become Fe + or three electrons to become Fe 1. Copper can lose either one electron to form Cu or two electrons to become Cu2+.

Although both aluminum and indium are in Group 13/III, aluminum forms A1J+ ions, whereas indium forms both In3+ and In+ ions. The tendency to form ions two units lower in charge than expected from the group number is called the inert-pair effect. Another example of the inert-pair effect is found in Group 14/IV tin forms tin(IV) oxide when heated in air, but the heavier lead atom loses only its two p-electrons and forms lead(II) oxide. Tin(II) oxide can be prepared, but it is readily oxidized to tin(IV) oxide (Fig. 1.56). Lead exhibits the inert-pair effect more strongly than tin. 

When numbering atoms in the chain, the lowest numbers are given preferentially to (a) functional groups named by suffixes (see Toolbox 19.1), (b) double bonds, (c) triple bonds, and (d) groups named by prefixes. 

Substituents replacing the hydrogen atom of an alcoholic hydroxy group of a saccharide or saccharide derivative are denoted as O-substituents. The 0- locant is not repeated for multiple replacements by the same atom or group. Number locants are used as necessary to specify the positions of substituents they are not required for compounds fully substituted by identical groups. Alternative periphrase names for esters, ethers, etc. may be useful for indexing purposes. For cyclic acetals see 2-Carb-28. 

The angular momenta of atoms are described by the quantum numbers L, S or J. When spin-orbit coupling is important, it is the total angular momentum J which is a constant of the system. A group of atomic wavefunctions with a common J value - akin to a term, as described in Section 3.6 - comprise (27 -i- 1) members with Mj... 

As holds for other cluster systems, certain magic cluster electron counts exist, which indicates for a certain cluster-halide ratio and interstitial present the filling of all bonding molecular orbitals and therefore the thermodynamically most stable situation. For main group interstitial atoms these are 14 cluster-based electrons whereas for transition-metal interstitials the magic number is 18 [1, 10-12]. All of these phases are synthesized by high-temperature solid-state chemical methods. A remarkable variety of different structure types has been... 

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