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scan0009 - 8.2 Ionic Bonding 311-ABLE 8.2 The Radius of...

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Unformatted text preview: 8.2 Ionic Bonding 311 -ABLE 8.2 The Radius of Some Common Ions and Atoms (in picometers) Group is removed from an atom, the amount of shielding is reduced. We say that the ef— fective nuclear charge experienced by each electron increases. The total number of electron—electron repulsions decreases, so the electrons are pulled closer to the nucleus. The net effect is a reduction in the size of the electron cloud around the cation. The size of the cation is less than the size of the atom (see Table 8.2). The opposite happens when an electron is added to an atom. The extra electron increases the number of electron—electron repulsions, thereby reducing the effective nuclear charge felt by each electron. This causes the electron cloud to swell in size. The anion, then, is larger than the atom from which itwas made. These effects continue as more electrons are removed from or added to an atom. All of the ions shown in Figure 8.7 have the same electron configuration, but they differ in the charge of the nucleus. We can see that as the nuclear charge increases, the size of the ion decreases. We noted that the removal of the first electron greatly decreases the size of an ion. Similar reasoning holds for the removal of subsequent electrons. In general, Na+ Mg2+ Al3+ 99 pm 65 pm 50 pm 3995.5, 27 The radii of a series of isoelectronic ions. ...
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