Electronic configuration, equivalent

Covalent bonding in F2 gives each fluonne eight electrons in its valence shell and a stable electron configuration equivalent to that of the noble gas neon... 

Only the electrons in an atom s valence shell are involved in covalent bonding. Fluorine, for example, has nine electrons, but only seven are in its valence shell. Pairing a valence electron of one fluorine atom with one of a second fluorine gives a fluorine molecule (F2) in which each fluorine has eight valence electrons and an electron configuration equivalent to that of the noble gas neon. Shared electrons count toward satisfying the octet of both atoms. 

To arrive at the electronic configuration of an atom the appropriate number of electrons are placed in the orbitals in order of energy, the orbitals of lower energy being filled first (Aufbau principle ), subject to the proviso that for a set of equivalent orbitals - say the three p orbitals in a set - the electrons are placed one... 

There are many compounds which do not conduct electricity when solid or fused indicating that the bonding is neither metallic nor ionic. Lewis, in 1916. suggested that in such cases bonding resulted from a sharing of electrons. In the formation of methane CH4 for example, carbon, electronic configuration l.s 2.s 2p. uses the tour electrons in the second quantum level to form four equivalent... 

Example The electron configuration for Be is Is lsfi but we write [He]2s where [He] is equivalent to all the electron orbitals in the helium atom. The Letters, s, p, d, and f designate the shape of the orbitals and the superscript gives the number of electrons in that orbital. 

In the excited electron configuration given, there are two electrons in partly filled orbitals, a Ad (electron 1) and a 5/ electron (electron 2). These are non-equivalent electrons (Section 7.1.2.3a) and we need consider only the coupling of the orbital angular momenta, fj andf2> and the spin angular momenta, Sj and S2-... 

CyclooctatetraenylCompounds. Sandwich-type complexes of cyclooctatetraene (COT), CgH g, are well known. The chemistry of thorium—COT complexes is similar to that of its Cp analogues in steric number and electronic configurations. Thorocene [12702-09-9], COT2Th, (16), the simplest of the COT derivatives, has been prepared by the interaction of ThCl [10026-08-1] and two equivalents of K CgHg. Thorocene derivatives with alkyl-, sdyl-, and aryl-substituted COT ligands have also been described. These compounds are thermally stable, air-sensitive, and appear to have substantial ionic character. 

Here, the bonding between carbon atoms is briefly reviewed fuller accounts can be found in many standard chemistry textbooks, e.g., [1]. The carbon atom [ground state electronic configuration (ls )(2s 2px2py)] can form sp sp and sp hybrid bonds as a result of promotion and hybridisation. There are four equivalent 2sp hybrid orbitals that are tetrahedrally oriented about the carbon atom and can form four equivalent tetrahedral a bonds by overlap with orbitals of other atoms. An example is the molecule ethane, CjH, where a Csp -Csp (or C-C) a bond is formed between two C atoms by overlap of sp orbitals, and three Csp -Hls a bonds are formed on each C atom. Fig. 1, Al. 

Electronic configuration = (2g6. Six-coordinate ionic radius = 73 pm (169). b Rate constant for the exchange of a particular coordinated solvent molecule. c All three H20 and MeCN are equivalent. 

The ground-state electron configuration of B suggests an ability to form one B—F bond, rather than three., JB JB -Jil I I Again, excitation, or promotion of an electron to a higher energy orbital, followed by hybridization is required to form three equivalent half-filled B orbitals. 

The electronic configuration (cuAB c)2(a)A Bc)2 of the Ai-B-iC hyperbonded unit may equivalently be expressed in terms of any orthogonal linear combination of the two occupied orbitals coAb c and coA Bc, such as... 

Divalent rare earth ions also have an outer electronic configuration of 4f"( including one more electron than for the equivalent trivalent rare earth). However, unlike that of (RE) + ions, the 4f " 5d excited configuration of divalent rare earth ions is not far from the 4f" fundamental configuration. As a result, 4f" 4f " 5d transitions can possibly occur in the optical range for divalent rare earth ions. They lead to intense (parity-allowed transitions) and broad absorption and emission bands. 

Again, if the two electrons are non-equivalent, all possible couplings arise (e.g., a % % 1 configuration yields 3A, 3E, 3E, JA, JE, and JE states). In contrast, if the two electrons are equivalent, certain of the term symbols are Pauli forbidden. Again, techniques for dealing with such cases are treated later in this Chapter. 

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