Electron Configurations of the Transition Metals and Their Ions

Electron Configurations of the Transition Metals and Their Ions 

Even though there are several exceptions, in general, the condensed ground-state electron configuration for the elements in each r/-block series is 

The partial (valence-level) electron configuration for the cf-block elements excludes the noble gas core and the filled inner / sublevel  

Transition metal ions form through the loss of the ns electrons before the (n - I)d electrons. Therefore, as one example, the electron configuration of Ti is [Ar] 3J, not [Ar] 45, and Ti is referred to as a d ion. Ions of different metals with the same configuration often have similar properties. For example, both Mn and Fe are d ions both have pale colors in aqueous solution and form complex ions with similar magnetic properties. 

SAMPLE PROBLEM 22.1 Writing Electron Configurations of Transition Metal 

Even though there are several exceptions, in general, the condensed ground-state electron configuration for the elements in each i-block series is [noble gas] nS n — l)d, with n = 4 to 7 and j = 1 to 10 In Periods 6 and 7, the condensed configuration includes the / sublevel  

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Electron Configurations of the Transition Metals and Their Ions 738 Atomic and Physical Properties of the Transition Hements 739 Chemical Properties of the Transition Elements 741... 

The energy separations between one set of orbitals and the next become smaller for As orbitals and beyond, and the relative energy ordering of these orbitals can actually vary among elements. These variations result in irregularities in the electron configurations of the transition metals and their ions (as we shall see later). 

Because the low-energy electronic configurations of d-block elements and their +1 ions are invariably of sdm form (see Table 2.2, Section 2.8), it is clear that both s and d orbitals will be involved in bond formation at transition-metal centers. What is less clear, a priori, is what role the valence p orbitals will play in bonding of the d-block elements. 

Table SI. 2 The electronic configuration of the 3d transition metals and their ions...

Figure 7.14 T shows the charges of some common ions. As we noted in Section 2.7, the charges of the alkali metals are always 1+ and those of the alkaline earth metals are always 2 -1- in their compounds. For each of fliese groups, flie outer s electrons are easily lost, yielding a noble-gas electron configuration. The charges of the transition metal ions do not follow an obvious pattern. Many transition-metal ions have 2+ charges, but l-i- and 3+ are also encountered. One of the characteristic features of the transition metals is their ability to form more tiian one positive ion. For example, iron may be 2-i- in some compounds and 3-r in others.

Electron configuration M 4s 3d 4s 3d 4s 3d 4s 3d 4s 3/ 4s 3d " The electron configurations of the first-row transition metals and their ions were discussed in Section 6.9 and Section 7.5, respectively. 

Recall from Section 8.7 that the transition metals form ions by losing electrons from the ns orbital before losing electrons from the (n - V)d orbitals. For example, Fe " has an electron configuration of [Ar] 3(f, because it has lost both of the 4i electrons to form the 2-1- charge. Examples 24.1 and 24.2 review the steps in writing electron configurations for transition metals and their ions. 

Zinc, cadmium and mercury are at the end of the transition series and have electron configurations ndw(n + l)s2 with filled d shells. They do not form any compound in which the d shell is other than full (unlike the metals Cu, Ag and Au of the preceding group) these metals therefore do not show the variable valence which is one of the characteristics of the transition metals. In this respect these metals are regarded as non-transition elements. They show, however, some resemblance to the d-metals for instance in their ability to form complexes (with NH3, amines, cyanide, halide ions, etc.). 

The d block transition metals are metals with an incomplete d subshell in at least one of their ions. Try to explain why Sc and Zn are often considered not to be transition metals. Consider the electronic configurations of the Fe + and Fe ions in both spectroscopic and orbital box notations. Use these notations to explain why Fe(lll) compounds are more stable than Fe(ll) compounds. 

Electron configurations of the elements of the three li-transition series are given in Table 25-1 and in Appendix B. Most li-transition metal ions have vacant d orbitals that can accept shares in electron pairs. Many act as Lewis acids by forming coordinate covalent bonds in coordination compounds (coordination complexes, or complex ions). Complexes of transition metal ions or molecules include cationic species (e.g., [Cr(OH2)( ]5+, [Co(NH3)g]3 +, [Ag(NH3)2]+), anionic species (e.g., [Ni(CN4)]2-, [MnCl ] ), and neutral species (e.g., [Fe(CO)5], [Pt(NH3)2Cl2]). Many complexes are very stable, as indicated by their low dissociation constants, (Section 20-6 and Appendix 1). 

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