Chemical properties of positive singly charged astatine ion in aqueous solution
The mobility of oxidized astatine in solutions H(Na)ClO4 (μ=0.4 M) − 1·10−4M K2Cr2O7 has been measured at 25°C in the interval 0.63≤pH≤1.68. Under these conditions astatine migrates to the cathode only. The speed of the migration depends upon the concentration of hydrogen ions in solution: pH 1.68 Uc = 1.17 · 10-4 cm2 V-1 s-1 pH 0.63 Uc = 2.67 · 10-4 cm2 V-1 s-1
The effect agrees with the opinion that the singly charged cation of astatine formed in acidic solutions is a strong aquacomplex [(H2O)xAt]+ (x=1–2) (protonated hypoastatic acid). Deprotonation constant of this cation is Kdp=0.032±0.005. Specific properties of the astatine cation are given. They can be explained, probably, through the peculiarities of its structure.