Electronegativity trends

Now let s compare atoms in the same column, for example, iodide (I ) and fluoride (F ). Here is where it gets a little bit tricky, because the trend is the opposite of the electronegativity trend ... 

The trend for AJ is in accord with the polarizability of the substituent atom, but opposite to the electronegativity trend. McLauchlan et al. 49> also studied a-CAN as a function of solvent and temperature. Their results, while differing in detail, are in accord with those of Goldstein s group. In a more recent study Goldstein et al. 5°) reexamined a-chloroacrylonitrile in detail in seven different... 

FIGURE 7.4 Electronegativity trends in the periodic table. Electronegativity increases from left to right and generally decreases from top to bottom. 

Explain the electronegativity trends across a row and down a column of the periodic table. Compare these trends with those of ionization energy and atomic radii. How are they all related ... 

The physical origin of these electronegativity trends is nuclear screening. As the atomic number increases from lithium to fluorine, the nuclear charge increases, as does... 

Because the nonbonding orbital is occupied, stability increases with s character, the converse of the situation for carbocations. The order of stability of carbanions is sp < sp < sp. The relative stability of gas phase carbanions can be assessed by the energy of their reaction with a proton, which is called proton affinity. The proton affinities of the prototypical hydrocarbons methane, ethene, and ethyne have been calculated at the MP4/6-31+G level/ The order is consistent with the electronegativity trends discussed in Section 1.1.5, and the larger gap between sp and sp, as compared to sp and sp, is also evident. The relative acidity of the hydrogen in terminal alkynes is one of the most characteristic features of this group of compounds. 

In general, how do electronegativity trends compare to trends of atomic size ... 

What is the electronegativity trend Where does hydrogen fit into the electronegativity trend for the other elements in the periodic table ... 

Plan Because we are not asked for quantitative answers, we can use the periodic table and our knowledge of electronegativity trends to answer the question. 

Note that these oxidation state rules are mainly based on electronegativity trends. The most electronegative atom in a compound is assigned a negative oxidation state, while the less electronegative atom(s) lose electrons and have positive oxidation states. 

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