Atomic scandium

For any cation, the empty 4 S orbital is slightly higher in energy than the partially filled 3 d orbital. Thus, the isoelectronic V and Cr cations both have the [Ar] 3 d configuration. On the other hand, the isoelectronic neutral atom scandium has the configuration [Ar]4 3 d ... 

It has been reported that ScBi2 has a tetragonal modification of the UBi2-type structure with lattice parameters of a = 5.22 A and c = 7.35 A with the space group of I4/mmm (Hamada et al., 1993 Paderno and Shitsevalova, 1995). Due to the small size of scandium as compared to the other rare earth atoms, scandium phases have been observed to form anomalous higher boride structures compared to the heavy lanthanides and yttrium, as will be discussed later in Sections 9 and 11. Small amounts of metal replacement for Sc in Sci xMxBi2 (x as small as 0.1, M = Y, Tm, Lu) have been reported to stabilize the structure in the normal cubic UBi2-type. 

Gallium [7440-55-3] atomic number 31, was discovered through a study of its spectral properties in 1875 by P. E. Lecoq de Boisbaudran and named from Gallia in honor of its discoverer s homeland. The first element to be discovered after the pubHcation of Mendeleev s Periodic Table, its discovery constituted a confirmation of the Table which was reinforced shordy after by the discoveries of scandium and germanium. 

Lanthanides is the name given collectively to the fifteen elements, also called the elements, ranging from lanthanum. La, atomic number 57, to lutetium, Lu, atomic number 71. The rare earths comprise lanthanides, yttrium, Y, atomic number 39, and scandium. Sc, atomic number 21. The most abundant member of the rare earths is cerium, Ce, atomic number 58 (see Ceriumand cerium compounds). 

The crystallographic radius assigned to the ion Fc+++ is comparable with that assigned to the scandium ion Sc+++. The ions K, Ca+t, and Sc+++ have the same number of electrons, and the same closed electronic shells as the argon atom. In aqueous solution there will be electrostatic forces of attraction between Ca++ and Cl, and between 8c+ t+ and Cl- but the quantum-mechanical forces between these ions will be forces of repulsion only. Between Fe+++ and Cl-, on the other hand, there may be quantum-mechanical forces of attraction. In view of the rather intense electrostatic attraction between Fe+++ and a negative ion, a 1 E. Rabinowitch and W. H. Stockmayer, J. Am. Chern. Soc., 64, 341 (1942). 

In fact this explanation for the configuration of the scandium atom and most other first transition elements is inconsistent. If the 3d... 

Goldschmidt has classed also with the ionic crystals the C-modification of the sesqui-oxides, cubic crystals with 16 M2O3 in the unit of structure. The inter-atomic distances reported by him are 2.16-2.20 A. for scandium oxide and 2.34-2.38 A. for yttrium oxide, in good agreement with the radius sums 2.21 A. for Sc+3-0= and 2.33 A. for Y+3-0". 

C02-0091. Each of the elements from chlorine to scandium has a nucleus with A = 40. Write correct atomic symbols for all these nuclei. 

The periodic table provides the answer. Each cut in the ribbon of the elements falls at the end of the p block. This indicates that when the n p orbitals are full, the next orbital to accept electrons is the ( + 1 )s orbital. For example, after filling the 3 orbitals from A1 (Z = 13) to Ar (Z = 18), the next element, potassium, has its final electron in the 4 S orbital rather than in one of the 3 d orbitals. According to the aufbau principle, this shows that the potassium atom is more stable with one electron in its 4 orbital than with one electron in one of its 3 (i orbitals. The 3 d orbitals fill after the 4 S orbital is full, starting with scandium (Z = 21). 

Fig.6. Same as fig.4 for 3d type orbitals (1=2, one radial node) of the Scandium atom.

Suppose we want to write the electron configuration of scandium (atomic number 21). We can rewrite the first 12 electrons that we wrote above for magnesium, and then just keep going. As we added electrons, we filled the first shell of electrons first, then the second shell. When we are filling the third shell, we have to ask if the electrons with n = 3 and / = 2 will enter before the n = 4 and 1 = 0 electrons. Since (n + /) for the former is 5 and that for the latter is 4, we must add the two electrons with n = 4 and / = 0 before the last 10 electrons with n = 3 and / = 2. In this discussion, the values of m and s tell us how many electrons can have the same set of n and / values, but do not matter as to which come first. 

Thus, scandium, atomic number 21, has two electrons in its Is subshell, two electrons in its 2s subshell, six electrons in its 2p subshell, two electrons in its 3s subshell, six electrons in its 3p subshell, two electrons in its 4s subshell, and its last electron in the 3d subshell. 

All the transition elements have large atomic numbers, the smallest (scandium) having 21 protons. All of them have at least four energy shells holding their electrons. Scientists do not know exactly why, but the transition element atoms often put electrons into a new, outer energy shell when some inner shells are not quite full. All the transition elements have one or two electrons in their outer shells, but from element to element each new electron is added to a shell deep inside the electron cloud. 

The strangest section of the periodic chart comes in the first transition subgroup. Under scandium and yttrium (marked with stars on the periodic chart) fall two long horizontal lists of elements so much alike that they are squeezed into two squares of the chart. Elements with the atomic numbers 57-71 are called the lanthanides. The actinides are elements with the atomic numbers 89-103, and they are all radioactive. These transition elements are as follows ... 

Cyclopentadienylamine)scandium(2,3-dimethyl-l,3-butadiene) 7 was synthesized in good yield, as shown in Scheme 2. Complex 7 reacted with benzonitrile to form a /rz-imido complex 8, the structure of which was characterized by single crystal X-ray diffraction. This product 8 was proposed to be formed by nitrile insertion followed by an attack of another diene methylene group on the carbon atom of the imido intermediate.3 An unsaturated metal imido species was formed, which easily dimerized to produce 8. However, the yield of 8 was not reported. 

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