First transition series ionic radii

Cations of the first transition series do not conform to the smooth pattern for the lanthanide elements shown in fig. 6.1. This is illustrated in fig. 6.2a by the radii of divalent cations in oxides containing transition metal ions in high-spin states. There is an overall decrease of octahedral ionic radius from Ca2+to Zn2+, but values first decrease to V2+, then rise to Mn2+, decrease to Ni2+, and rise again to Zn2+. The characteristic double-humped curve shown in fig. 6.2a has... 

Use the Handbook of Chemistry and Physics or a suitable website to find the Crystal Ionic Radii of the Elements. Plot atomic number versus radius of the 2 + ions of the first -transition series. Is there a trend Is a minimum size formed during the transition from Sc to Zn Do the values for the second and third -transition series appear to form a similar minimum at about the same group number ... 

Prediction of Structural Changes. Crystal field theory is frequently applied to account for and even predict structural and chemical changes. A well-known example is the variation of first row transition metal ionic radii in an octahedral environment as illustrated in Figure 6-38 [50], The dashed line connects the points for Ca, Mn, and Zn, i.e., atoms with spherically symmetrical distribution of d electrons. Since the shielding of one d electron by another is imperfect, a contraction in the ionic radius is expected along this series. This in itself would account only for a steady decrease in the radii, whereas the ionic radii of all the other atoms are smaller than interpolation from the Ca-Mn-Zn curve would suggest. As is well known, the... 

The following ionic radii (in angstroms) are estimated for the +2 ions of selected elements of the first transition-metal series, based on the structures of their oxides Ca (0.99), TP+(0.71), V +(0.64), Mn +(0.80), Fe +(0.75), Co +(0.72), Ni (0.69), Cu (0.71), Zn (0.74). Draw a graph of ionic radius versus atomic number in this series, and account for its shape. The oxides take the rock salt structure. Are these solids better described as high- or low-spin transition-metal complexes ... 

---