59. In Example 1.8, there are two effects that are responsible for the discrepan
ID: 714474 • Letter: 5
Question
59. In Example 1.8, there are two effects that are responsible for the discrepancy between the Z" calculated from Slater's rules and the Z calculated from the Pauling electronegativity of Au. (a) Name these two effocts and describe them in terms of penetration or shielding. (b) For each of the two causes, tell whether the discrepancy should be the same, worse, or less for the element below gold. Overall, would you expect the electronegativity of this "eka-gold" to be greater than, less than, or equal to 2.54? (c) Name an element in an entirely different group of the periodic table to which the chemistry of eka-gold might be more related (than it would be to the chemistry of copper in Group 11).Explanation / Answer
Pauling established Electronegativity as the "power" of an atom in a molecule to attract electron to itself. It is a measure of the atom's ability to attract electron to itself while the electron is still attached to another atom. The higher the values, the more likely that atom can pull electron from another atom and into itself. Electronegativity correlates with bond polarity,ionization energy, electron affinity, effective nuclear charge, and atomic size.
The periodic trend for electronegativity generally increases from left to right and decreases as it go down the group. The exception are Hydrogen and the noble gases because the noble gases are content with their filled outermost shells, and hydrogen cannot bear to lose a valence electron unlike the rest of the group 1 metals. The elements in the halogen group usually have the highest electronegativity values because they only need to attract one valence electron to complete the octet in their outer shell. Whereas the group 1 elements except for Hydrogen, are willing to give up their only valence electron so they can fulfill having a complete, filled outer shell.
Slater's rules:
Slater's rules are rules that provides the values for the effective nuclear charge concept, or Zeff. These rules are based on experimental data for electron promotion and ionization energies, and Zeff is determined from this equation:
Zeff = Z S
Where
Through this equation, this tells us that electron may get reduced nuclear charge due to high shielding. Allred and Rochow used Zeff because it is accurate due to the involvement of shielding that prevents electron to reach its true nuclear charge: Z. When an atom with filled s-shell attracts electrons, those electrons will go to the unfilled p-orbital. Since the electrons have the same negative charge, they will not only repel each other, but also repel the electrons from the filled s-shell. This creates a shielding effect where the inner core electrons will shield the outer core electrons from the nucleus. Not only would the outer core electrons experience effective nuclear charge, but it will make them easily removed from the outer shell. Thus, It is easier for outer electrons to penetrate the p shell, which has little likelihood of being near the nuclear, rather than the s shell. Consider this, each of the outer electron in the (ns, np) group contributes S = 0.35, S = 0.85 in the (n - 1) shell, and S = 1.00 in the (n - 2) or lower shells.
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