Hafnium atomic radius

These are listed in Table 2.3 and shown in Figure 2.4. It will be seen that the atomic radii exhibit a smooth trend across the series with the exception of the elements europium and ytterbium. Otherwise the lanthanides have atomic radii intermediate between those of barium in Group 2A and hafnium in Group 4A, as expected if they are represented as Ln + (e )3. Because the screening ability of the f electrons is poor, the effective nuclear charge experienced by the outer electrons increases with increasing atomic number, so that the atomic radius would be expected to decrease, as is observed. Eu and Yb are exceptions to this because of the tendency of these elements to adopt the (+2) state, they have the structure [Ln +(e )2] with consequently greater radii, rather similar to barium. In contrast, the ionic radii of the Ln + ions exhibit a smooth decrease as the series is crossed. 

We expect the atomic radius to increase down a group in the periodic table. Can you suggest why the atomic radius of hafnium breaks this rule (See the following data.)... 

Zirconium and hafnium are the group 4B elements in the second and third transition series. The atomic radii of these elements are virtually the same (Figure 23.22). Explain this similarity in atomic radius. 

In the sixth period, the/-block elements fall between lanthanum (Group 3) and hafnium (Group 4). Because of the increase in atomic number that occurs firom lanthanum to hafnium, the atomic radius of hafnium is actually sUghtiy less than that of zirconium, Zr, the element immediately above it The radii of elements following hafnimn in the sixth period vary with increasing atomic number in the usual maimer. 

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