4.2 Occurrence, Preparation, and Properties of Transition Metals and Their Compo
4.2 Occurrence, Preparation, and Properties of Transition Metals and Their Compounds
Transition metals are defined as those elements that have (or readily form) partially filled d orbitals. As shown in (Figure 4.2.1), the d-block elements in groups 3–11 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals. The d orbitals fill with the copper family (group 11); for this reason, the next family (group 12) are technically not transition elements. However, the group 12 elements do display some of the same chemical properties and are commonly included in discussions of transition metals. Some chemists do treat the group 12 elements as transition metals.
The d-block elements are divided into the first transition series (the elements Sc through Cu), the second transition series (the elements Y through Ag), and the third transition series (the element La and the elements Hf through Au). Actinium, Ac, is the first member of the fourth transition series, which also includes Rf through Rg.
The f-block elements are the elements Ce through Lu, which constitute the lanthanide series (or lanthanoid series), and the elements Th through Lr, which constitute the actinide series (or actinoid series). Because lanthanum behaves very much like the lanthanide elements, it is considered a lanthanide element, even though its electron configuration makes it the first member of the third transition series. Similarly, the behavior of actinium means it is part of the actinide series, although its electron configuration makes it the first member of the fourth transition series.
Activity 4.2.1 – Valence Electrons in Transition Metals
(1) Review how to write electron configurations, covered in the chapter on electronic structure and periodic properties of elements. Recall that for the transition and inner transition metals, it is necessary to remove the s electrons before the d or f electrons. Then, for each ion, give the electron configuration:
(1a) cerium(III)
(1b) lead(II)
(1c) Ti2+
(1d) Am3+
(1e) Pd2+
For the examples that are transition metals, determine to which series they belong.
Solution
(2) For ions, the s-valence electrons are lost prior to the d or f electrons.
(2a) Ce3+[Xe]4f1; Ce3+ is an inner transition element in the lanthanide series.
(2b) Pb2+[Xe]6s25d104f14; the electrons are lost from the p orbital. This is a main group element.
(2c) titanium(II) [Ar]3d2; first transition series
(2d) americium(III) [Rn]5f6; actinide
(2e) palladium(II) [Kr]4d8; second transition series
Check Your Learning
Give an example of an ion from the first transition series with no d electrons.
Answer
V5+ is one possibility. Other examples include Sc3+, Ti4+, Cr6+, and Mn7+.
Uses of Lanthanides in Devices
Lanthanides (elements 57–71) are fairly abundant in the earth’s crust, despite their historic characterization as rare earth element