Periodic Trends and Charge Density

A summary of trends in atomic radius, first ionization energy, electron affinity, electronegativity, and atomic polarizability 

In equation (21.1), the numerator represents the total charge, in coulombs, of the cation the denominator represents the volume of the cation, which is assumed to be spherical. If the ionic radius is expressed in millimeters, then 

A FIGURE 21-2 Polarization of the electron cloud of an anion by a cation 

A cation with a high charge density distorts the electron cloud around the anion. The undistorted electron cloud is shown with a dashed line and the distorted electron cloud is shown with a solid line. The greater the distortion of the electron cloud, the greater the degree of covalency of the bond between the anion and cation. 

Source Data from the CRC Handbook of Chemistry and Physics, 95th ed. 

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