Group , periodic inner transition

Groups or families are the vertical rows on the periodic table. They may be labeled in two ways. The older way involves a Roman numeral and a letter, either A or B. We call the groups labeled with an A the main-group elements, while the B groups are the transition elements. Two horizontal groups, the inner transition elements, belonging to periods 6 and 7 are normally pulled out of the main body of the periodic table and are placed at the bottom of the table. 

The three series of elements arising from the filling of the 3d, 4d and 5d shells, and situated in the periodic table following the alkaline earth metals, are commonly described as transition elements , though this term is sometimes also extended to include the lanthanide and actinide (or inner transition) elements. They exhibit a number of characteristic properties which together distinguish them from other groups of elements ... 

There are three distinct areas of the periodic table—the main group elements, the transition group elements, and the inner transition group elements. We will focus our attention at first on the main group elements, whose properties are easiest to learn and to understand. 

The rules above gave maximum and minimum oxidation numbers, but those might not be the only oxidation numbers or even the most important oxidation numbers for an element. Elements of the last six groups of the periodic table for example may have several oxidation numbers in their compounds, most of which vary from each other in steps of 2. For example, the major oxidation states of chlorine in its compounds are -1, +1, +3, +5, and +7. The transition metals have oxidation numbers that may vary from each other in steps of 1. The inner transition elements mostly form oxidation states of + 3, but the first part of the actinoid series acts more like transition elements and the elements have... 

The 3rd group of the Periodic Table (the 1st column within the block of the transition elements) contains the metals scandium, yttrium, lanthanum, and actinium. Lanthanum (atomic number 57) may be considered the earliest member of the family of metals, called lanthanides (general symbol Ln), forming, inside the principal transition series, an inner transition series (up to atomic number 71). Scandium and yttrium together with the lanthanides are also called rare earth metals (general symbol R). 

The /block includes all the inner transition elements. Atoms of /block elements have filled s orbitals in the outer energy levels, as well as filled or partially filled 4/and 5/orbitals. In general, the notation for the orbital filling sequence is ns, followed by (n - 2)/, followed by (n - l]d, followed by (for period 6 elements) np. However, there are many exceptions that make it difficult to predict electron configurations. Because there are seven/orbitals, with a maximum of fourteen electrons, the /block spans fourteen groups. 

Inserting the inner transition metals between atomic groups 3 and 4 results in a periodic table that is not easy to fit on a standard sheet of paper. 

The members of the d block, with the exception of the elements in Group 12 (the zinc group) are called transition metals. As we shall see, these elements are transitional in character between the vigorously reactive metals in the s block and the less reactive metals on the left of the p block. The members of the f block, which is shown below the main table (to save space), are the inner transition metals. The upper row of this block, following lanthanum (element 57) in Period 6, consists of the lanthanides and the lower row, following actinium (element 89) in Period 7, consists of the actinides. 

FIGURE 20.1 Thetransi- tion elements (d-block elements, shown in yellow) are located in the central region of the periodic table between the s-block and p-block main-group elements. The two series of inner transition elements (/-block elements, shown in green) follow lanthanum and actinium. 

Within the B group transition elements are two horizontal series of elements called inner transition elements. They usually appear below the main periodic table. Notice, however, that they fit between the elements in Group 3 (NIB) and Group 4 (IVB). 

Another major classification of the elements in terms of the periodic table is shown in Figure 1.7. Three areas are defined and named the main group elements, the transition elements, and the inner transition elements. The main group elements are the simplest to learn abont, and they will be stndied first. The transition elements inclnde some of the most important elements in onr everyday lives, such as iron, nickel, chrominm, zinc, and copper. The transition elements are often divided into four rows of elements, called the first, second, third, and fourth transition series. The elements of the fourth transition series except for actinium (Ac), and those of the main group elements above 112, are artificial they are not found in nature. The two inner transition series fit into the periodic table in periods 6 and 7, right after lanthanum (La) and actinium (Ac), respectively. The inner transition elements include a few important elements, including uranium and plutonium. The first series of inner transition elements is called the lanthanide series, after lanthanum, the element that precedes... 

The periodic table is a classification scheme for elements that is tremendously useful in learning the properties of the elements. It consists of seven periods and 16 classical groups, or families (18 in a more modem but less useful version). Several of the groups have names, which beginning students need to leam. The elements are separated into metals and nonmetals on the periodic table. They are also subdivided into main group elements, transition elements, and inner transition elements. (Section 1.5)... 

The properties of the elements stem from their electronic configurations, and the properties place them in their locations in the periodic table. In each group, the elements have a characteristic outermost electronic configuration. The existence of the transition and inner transition elements stems from adding electrons to inner shells after outer shells have been started. Because the periodic table reflects the electronic structures of the atoms, it can be used as a memory device when writing electronic configurations. The ability to write and understand such configurations is a very important skill. (Section 4.8)... 

Inner transition groups Fig. 4-8. Periodic table as an aid to assigning electronic confignrations... 

Transition-metal 7i-cyclopentadienyl complexes are known for all of the naturally occurring transition and inner transition metals and representative examples are grouped below according to their positions in the periodic chart. For the sake of brevity, most of the work involving monosubstituted cyclopentadienyl and mixed-sandwich (i.e., cyclopentadienyl-metalloboranes ) complexes has been excluded. 

Periodic group I II Transition group III IV V VI VII VIII Configurations of inner shells... 

The group B elements, or transition elements, are divided into transition metals and inner transition metals. The two sets of inner transition metals, known as the lanthanide and actinide series, are located along the bottom of the periodic table. The rest of the group B elements make up the transition metals. Elements from the lanthanide series are used extensively as phosphors, substances that emit light when struck by electrons. The How It Works at the end of the chapter explains more about phosphors and how images are formed on a television screen. 

Beginning with period 4, the periodic table is expanded to make room for the elements whose d or f orbitals are being filled. These elements are called transition elements. They are subdivided into d-block and f-block elements—the transition metals and inner transition metals, respectively. Note that the groups of transition elements are labeled B to distinguish them from the groups containing representative elements. Recall that a transition metal is any element whose final electron enters a d sublevel. An inner transition metal is any element whose final electron enters an f sublevel. 

The inner transition metals are divided into two groups the period 6 lanthanide series and the period 7 actinide series. 

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