Effective nuclear charge The

Later methods, especially that of Gordy (1955), and later Allred and Rochow (1958) make use of screening constants of the electron strucmre for the nuclear charge of each atom. This determines die attraction between the nucleus of the atom and an electron outside the normal electron complement, and is die effective nuclear charge. The empirical equation for the values of electronegativity obtained in this manner by Allred and Rochow is... 

Effective nuclear charge The nuclear charge experienced by outer-shell electrons, diminished by the shielding effect of inner-shell electrons. 

A general decline in atomic size is another consequence of increasing effective nuclear charge. The figure above also shows the ionic radii of M2+ ions of the 3d series. 

There are two factors that are closely associated with the structure and behavior of atoms. The first of these is known as effective nuclear charge. The nuclear charge is related to the number of charged particles (protons) in the nucleus. As the nuclear charge increases, there is an increase in the attractive force between the nucleus and the electrons. Nuclear charge increases from left to right across a period. 

E = me2 Einstein s equation proposing that energy has mass E is energy, m is mass, and c is the speed of light. (12.2) Effective nuclear charge the apparent nuclear charge exerted on a particular electron, equal to the actual nuclear charge minus the effect of electron repulsions. (12.11)... 

Changes in Z ff. As the effective nuclear charge —the positive charge felt by an electron—increases, outer electrons are pulled closer to the nucleus thus, the atoms are smaller. 

When the platinum nucleophilicity scale was first proposed it was implied that one np, scale was applicable to all substrates and that plots of logk2 against npt°(Y) were linear, taking the form log 10 2 = S np, (Y) + C, where S is termed the nucleophilic discrimination factor of the substrate and C its intrinsic reactivity. Discussions of mechanism based on a comparison of nucleophilic discrimination factors are frequently encountered. Nucleophiles that do not retain their positions in the nucleophilicity scale, e.g. NO2", SeCN and SC(NH2)2, were termed biphilic by Cattahni since their behaviour could be explained by their n-acceptor properties. When the Pt reaction centre had a greater n-basicity than the standard complex (for example a smaller effective nuclear charge) the substrate was more reactive than predicted and vice versa. This concept had been deduced some years earlier by Bosnich from his work with octahedral Ru complexes... 

The larger the effective nuclear charge, the more strongly the electrons are held and the smaller the atomic radius. For the second period, the atomic radius of Li is largest because the 2s electron is well shielded by the filled l5 shell. The effective nuclear charge that the outermost electrons feel increases across the period as a result of incomplete shielding by electrorrs in the same shell. Consequently, the orbital containing the electrons is compressed and the atomic radius decreases. 

The larger the effective nuclear charge, the more tightly held are the electrons. Thus, the atomic radius will be small, and the ionization energy will be large. The quantities show an opposite periodic trend. 

A FIGURE 7.2 Effective nuclear charge. The effective nuciear charge experienced by the vaience eiectron in a sodium atom depends mostiy on the 11 + charge of the nucieus and the 10- charge of the core eiectrons. 

Which will experience the greater effective nuclear charge, the electrons in the n = 3 shell in Ar or the n = 3 shell in Kr Which will be closer to the nucleus Explain. 

The MIEs increase monotonically across each period, presumably because of the increasing effective nuclear charge. The ionization energy then drops sharply as each new period begins with an alkali metal, presumably because of the increase of the principal quantum number n (the last electron has entered a new shell at a larger distance from the nucleus) and a decreased effective nuclear charge. 

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