Ions ionic radius

Ion Ionic radius, pm CoUoidal hydrous manganese dioxide, mol/mol Hydrated radius, pm 5-Mn02, )J.mol/g... 

Metal ion Ionic radius Oxalate Malonate Difference... 

HOST-GUEST INTERACTIONS VANADATE ION IONIC RADIUS... 

Ion Ionic radius Coordination munber Typical geometry of inner-sphere complex First pA a of [M(H20) ] + , 2 22... 

Ion Ionic radius (A) Hydration free energy in keal mol i(kJ mofi)... 

Ion Ionic Radius (A) Charge/Radius Ratio Hydration Energy (kj/mol)... 

It is clear that, if available, monocations such as potassium and sodium will be incorporated into a quadruplex. The potassium and ammonium ions are too large to be coordinated by a single G-quartet in a coplanar fashion. As a result, coordination of these ions occurs between two G-quartets planes. Each quadruplex involving n quartets will then accommodate n — 1) of these specific ions. For example, quantitative determination of ammonium peak intensity revealed that three NH4 ions are placed between four quartets. In contrast, the smaller Na" ion (ionic radius of 1.18 A) allows for in-plane coordination. Multiple Na" ions are therefore not restricted to the spacing between G-quartets, and can move further away form each other to reduce electrostatic repulsions. In any case, empty sites between quartets are probably very rare. In fact, although vacant coordination sites are likely to exist (as ions move between sites, see below), their lifetime must be very short as demonstrated, for example, by Federiconi et who determined a site occupancy of 0.97 K " ions per tetramer in GMP quadruplexes prepared in 0.5 M KCl. 

In fact, trigonal holes are so small that they are never occupied in binary ionic compounds. Whether the tetrahedral or octahedral holes in a given binary ionic solid are occupied depends mainly on the relative sizes of the anion and cation. For example, in zinc sulfide the ions (ionic radius = 180 pm) are arranged in a cubic closest packed structure with the smaller ions (ionic radius = 70 pm) in the tetrahedral holes. The locations of the tetrahedral holes in the face-centered cubic unit cell of the ccp structure are shown in Fig. 10.36(a). Note from this figure that there are eight tetrahedral holes in the unit cell. Also recall from the discussion in Section 10.4 that there are four net spheres in the face-centered cubic unit cell. Thus there are twice as many tetrahedral holes as packed anions in the closest packed structure. Zinc sulfide must have the same number of S ions and Zn ions to achieve electrical neutrality. Thus in the zinc sulfide structure only half the tetrahedral holes contain Zn ions, as shown in Fig. 10.36(c). 

Ion Ionic radius kf Hydrated radius(k) Ionic volume (A ) Hydrated volume (A ) Coordination number Water exchange rate(s ) ... 

Complex Coordination number of metal ion Ionic radius (A) Macrocycle fold angle (deg) Ref. ... 

The calculated values of displacements for ions of the first eight coordinational shells of impurity ions in the LiTmF4 crystal are given in table 19. As expected, the displacements of the nearest neighbours of impurities are maximal and they correlate with the excess of the impurity ionic radii over that of Tm + ion [ionic radius of Tm equals 0.99 A Lu +, 0.97 A Nd +, 1.12A (Kaminskii 1975)]. It is seen that the ionic displacements do not decrease monotonously with the increase of the distance from an impurity ion. 

Atomic Number Symbol Atomic Radius (nm) Ion Ionic Radius (nm)... 

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