Effective atomic number also

The effective atomic number rule (the 18-electron rule) was described briefly in Chapter 16, but we will consider it again here because it is so useful when discussing carbonyl and olefin complexes. The composition of stable binary metal carbonyls is largely predictable by the effective atomic number (EAN) rule, or the "18-electron rule" as it is also known. Stated in the simplest terms, the EAN rule predicts that a metal in the zero or other low oxidation state will gain electrons from a sufficient number of ligands so that the metal will achieve the electron configuration of the next noble gas. For the first-row transition metals, this means the krypton configuration with a total of 36 electrons. 

The sensitivity of Z contrast for the detection of small clusters depends not only on the signal Z dependence, but also depends on the microscope resolution, which is governed by the probe size 6. A small cluster containing N atoms of atomic number Zi, supported on a film of effective atomic number Z2 of thickness t, will have a contrast in the annular detector signal given by... 

Dual-energy is a CT imaging approach aimed at generating and extracting additional information beyond material density from image slices. The additional information, a second material property, is known as the effective atomic number, Zeff. Although the X-ray attenuation coefficient is proportional to a material s density p, it is also a function (i) of the atomic number Z of each of the material s... 

The effective atomic number (EAN) rule is useful for interpreting how ligands with more than one double bond are attached to the metal. Essentially, each double bond that is coordinated to the metal functions as an electron pair donor. Among the most interesting olefin complexes are those that also contain CO as ligands. Metal olefin complexes are frequently prepared from metal carbonyls that undergo substitution reactions. 

Teo s topological approach also deserves mention in this section. It combines Euler s theorem with the idea of an effective atomic number rule for each cluster vertex, but involves a rather arbitrary parameter whose purpose is to correct for the formation of multicenter bonds. 

Also called the effective atomic number (EAN) rule. 

In addition to the 18- and 16-electron rules, there is also the Effective Atomic Number (EAN) rule, which looks to the periodic table for verification of what can be calculated using the 18-electron rule. To put this rule simply, it says that an organometallic complex (as a system) binds as many ligands as possible to reach the number of electrons of the next noble gas configuration. 

The above interchange (effective) atomic number through which the chemical (reactive) state is associated with lower charge respecting the physical state may be also be found at the energetic level based on quantum equation (4.143), as specialized for the two branches of Figure 4.6 for the N Z) dependence. Thus, the chemical (reactive) state takes the analytic form (Putz, 2012a)... 

A variety of metal carbonyls are known. The eighteen-electron rule and Sidgwick s effective atomic number rule (Section 2.3) are very successful in explaining their stoichiometries. Simple monomeric carbonyls are expected for transition metals with even atomic numbers Cr(CO)6, Fe(CO)s, Ni(CO)4. The heavier members of the Cr and Fe families also form monomeric carbonyls of the predicted stoichiometry. 

From your study of general chemistry, you may already be familiar with the concept that an electron has a spin and that a spinning charge creates an associated magnetic field. In effect, an electron behaves as if it is a tiny bar magnet. An atomic nucleus that has an odd mass or an odd atomic number also has a spin and behaves as if it is a tiny bar magnet. Recall that when designating isotopes, a superscript represents the mass of the element. 

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