Scandium oxidation state

We may note (a) the common occurrence of oxidation state +2 where the 4s electrons have been formally lost, (b) the increase in the number of oxidation states from scandium to manganese in the latter element, the oxidation state + 7 corresponds to the formal loss of the and 3d electrons, (c) the sharp decrease in the number of oxidation states after manganese—suggesting that removal of the paired id electrons is less easy (d) the oxidation state 0, occurring for many of the later elements in the series. ... 

Scandium is not an uncommon element, but is difficult to extract. The only oxidation state in its compounds is -I- 3, where it has formally lost the 3d 4s electrons, and it shows virtually no transition characteristics. In fact, its chemistry is very similar to that of aluminium (for example hydrous oxide SC2O3, amphoteric forms a complex [ScFg] chloride SCCI3 hydrolysed by water). 

The maximum oxidation state observed for the elements first increases and then decreases as we go across the transition row. Thus we have 4-3 for scandium, 4-4 for titanium, 4-5 for vanadium, 4-6 for chromium, and 4-7 for manganese. The 4-7 represents the highest value observed for this transition row. After manganese, the maximum value diminishes as we continue toward the end of the transition row. 

Except for the elements at the ends of the rows, each transition metal can exist in several different oxidation states. The oxidation states displayed by the 3d transition metals are shown in Table 20-1. The most important oxidation states are highlighted in the table. The most common oxidation state for the 3d transition metals is +2, known for all the elements except Sc. Chromium, iron, and cobalt are also stable in the +3 oxidation state, and for vanadium and manganese the -H4 oxidation state is stable. Elements from scandium to manganese have a particularly stable oxidation state corresponding to the loss of ah the valence electrons configuration). 

The lanthanides are congeners of the Group IIIA metals scandium and yttrium, with the +3 oxidation state usually being the most stable. These ions are strong oxyphilic Lewis acids and catalyze carbonyl addition reactions by a number of nucleophiles. Recent years have seen the development of synthetic procedures involving lanthanide metals, especially cerium.195 In the synthetic context, organocerium... 

The series of 3d elements from scandium to iron as well as nickel preferably form octahedral complexes in the oxidation states I, II, III, and IV. Octahedra and tetrahe-dra are known for cobalt, and tetrahedra for zinc and copper . Copper(II) (d9) forms Jahn-Teller distorted octahedra and tetrahedra. With higher oxidation states (= smaller ionic radii) and larger ligands the tendency to form tetrahedra increases. For vanadium(V), chromium(VI) and manganese(VII) almost only tetrahedral coordination is known (VF5 is an exception). Nickel(II) low-spin complexes (d8) can be either octahedral or square. 

Scandium is the first element in the fourth period of the transition elements, which means that the number of protons in their nuclei increases across the period. As with all the transition elements, electrons in scandium are added to an incomplete inner shell rather than to the outer valence shell as with most other elements. This characteristic of using electrons in an inner shell results in the number of valence electrons being similar for these transition elements although the transition elements may have different oxidation states. This is also why all the transition elements exhibit similar chemical activity. 

Not very many compounds of scandium have been found or produced. It has an oxidation state of +3, thus its metallic ion is Sc which means it combines with anions with a -1 oxidation state as follows ... 

When scandium ions react with anions with a -2 oxidation state, different compounds result, including, for example, the following two compounds ... 

Scandium forms all its compounds in 3+ oxidation state. This is the only valence known for the metal. These compounds include the oxide, SC2O3 hydroxide, Sc(OH)3 chloride, ScCls fluoride, ScFs sulfate, Sc2(S04)3, and the nitrate salt, Sc(N03)s. 

This chapter consists of a description of the ions formed in aqueous solutions by the transition elements - the d-block elements - and a discussion of the variations of their redox properties across the Periodic Table from Group 3 to Group 12. There is particular emphasis on the first transition series from scandium to zinc in the fourth period, with summaries of the solution chemistry of the second (Y to Cd) and third (Lu to Hg) series. The d-block ions in solution are those restricted solely to aqua complexes of cations, e.g. [Fe(H20)f,]" +, and the various oxocalions and oxoanions formed, e.g. V02+ and MnCXj". Oxidation states that are not well characterized are omitted or referred to as such. 

F. T. Edelmann, Scandium, yttrium and the lanthanide and actinide elements, excluding their zero oxidation state complexes in Comprehensive Organometallic Chemistry II (eds. E. W. Abel, EG. A. Stone and G. Wilkinson), Elsevier, Oxford, 1995, vol. 4 (ed.M.F. Lappert), ch. 2. 

There are a number of solid phases of the types MScCl and ScCl where the formal oxidation state of scandium is less than three. They are usually made by direct combination at elevated temperatures of MCI, ScCl3 and metallic scandium. Their structures often show evidence of Sc—Sc bonds. Thus CsScCl3 is made by action of Sc on Cs3Sc2Cly at 700 °C. The shiny blue product has the hexagonal perovskite CsNiCl3 structure. This is similar to the Cs3Sc2Cl9 structure but with all Sc positions filled. Non-stoichiometric phases exist between the two end structures.128 When scandium is heated with ScCl3 at 940-960 °C in a sealed Ta... 

Most d-block elements have more than one common oxidation state (Fig. 16.7). The distribution of oxidation states looks daunting at first sight, but there is a pattern. Except for mercury, the elements at the ends of each row of the d block occur in only one oxidation state other than 0. Scandium, for example, is found only in oxidation state +3, and zinc only as +2. All the other elements of each row have at least two oxidation states. Copper, for example, is found in two oxidation states, +1 (as in CuCl) and +2 (as in CuCl2). Elements close to the center of each row have the widest range of oxidation states. Manganese, at the center of its row, has seven oxidation states. Elements in the second and third rows of the block are more likely to reach higher oxidation states than those in the first row. 

The subsequent fate of the perchlorate depends on the temperature. At relatively low temperatures it is stable and thus remains. At temperatures high enough for it to decompose, the final products are chloride and oxygen. When the metal exists in more than one oxidation state, the oxide may form. The chlorates of the rare earths, scandium, and yttrium form oxychlorides. 

Transition elements. Elements of the first transition series are characterized by having incompletely filled 3d orbitals in one or more of their common oxidation states. The series includes scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper, which have electronic configurations of the form (ls)2(2s)2(2p)6(3s)2(3p)6(3[Pg.41]

Scandium oxide is a refractory white solid (mp 3100 °C) formed on ignition of either the metal or appropriate compounds such as the nitrate, sulfate, and hydroxide. It has amphoteric tendencies denoted by its solubihty in excess alkali from which compounds like K3[Sc(OH)6], containing octahedrally coordinated scandium, have been isolated. In the solid state it has six-coordinate scandium in the Mu203 structure. 

F. G. N. Cloke, Zero Oxidation State Complexes of Scandium, Yttrium and the Lanthanide Elements, in Comprehensive Organometallic Chemistry IF, eds. F. G. A. Stone, G. Wilkinson, and E. W. Abel, Pergamon Press, Oxford, 1995, Vol. 4, Chap. 1 p. 1. 

In addition to the maximum values attainable, the variety of oxidation states for which compounds can be isolated is of importance. Among the first-row oxides, scandium in Group 3 and zinc in Group 12 appear in only the group oxidation state. In the second and third row, zirconium... 

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