Representative elements The A group

Group designations are traditionally given on the periodic table for the ri-block transition metals (Fig. 20.1). However, these designations do not relate as directly to the chemical behavior of these, elements as do the designations for the representative elements (the A groups), so we will not use them. 

Representative Elements. The A group elements in the periodic table are called representative elements. Their last electron is assigned to an outer shell s or p orbital. These elements show distinct and fairly regular variations in their properties with changes in atomic number. 

Representative elements The A group elements in the periodic table. 

Table 9.1 contains a summary of recycling efficiencies for a variety of representative elements. The results fall into three groups, which have been termed biolimiting, biointermediate, and biounlimited. The biolimiting elements have 1 and, thus, are almost... 

If a set of objects is such that operation on any of them by any element of a group produces a linear combination of the same set of elements, then the operations can be expressed in terms of a set of matrices that represent the... 

The trace of a matrix which represents an element of a group (or an operation of a point group) is called a character and is usually given the symbol X- X(R) is thus the character of the operation R in the representation which has matrices D(R)> i.e. 

Do you see the pattern For the representative elements, the number of valence electrons is equal to the group number. This is why the authors believe the older AB numbering system for the periodic table is superior to the serial (1-18) numbering system. For the A-group elements, the number of valence electrons is equal to the group number. The B-group elements, or transition elements, are not as easy, and we will skip them for the purposes of our discussion. 

The periodic table. The elements in the A groups are the representative elements. The elements shown in pink are called transition metals. The dark line approximately separates the nonmetals from the metals. The elements that have both metallic and nonmetallic properties (semimetals) are shaded in blue. 

Elements in any given group on the periodic table have the same number of valence electrons. The number and location of valence electrons determine the chemistry of an element. Thus, elements within a group have similar physical and chemical properties. Representative elements display the range of possible valence electrons from one in group lAto eight in group 8A. The valence electrons of representative elements are in s or p orbitals. 

There are eight groups of representative elements, or main-group elements. In addition to the representative elements, there are ten groups (and three periods) of transition-metal elements, a period of elements with atomic numbers 57 through 71 called the rare-earth or lanthanide elements, and a period of elements from atomic numbers 89 through 103 called the actinides, all of which are unstable and... 

One factor that favors an atom of a representative element forming a monatomic ion in a compound is the formation of a stable noble gas electron configuration. Energy considerations are consistent with this observation. For example, as one mole of Li from Group LA forms one mole of Li+ ions, it absorbs 520 kj per mole of Li atoms. The IE2 value is 14 times greater, 7298 kj/mol, and is prohibitively large for the formation of Li + ions under ordinary conditions. For LE+ ions to form, an electron would have to be removed from the filled first shell. We recognize that this is unlikely. The other alkali metals behave in the same way, for similar reasons. 

The representative elements are those in the A groups of the periodic table. 

In this chapter we will discuss some representative metals and some /-transition metals. The representative elements are those in the A groups of the periodic table. They have valence electrons in their outermost s and p atomic orhitals. Metallic character increases from top to bottom within groups and from right to left within periods. All the elements in Groups lA (except H) and TTA are metals. The heavier members of Groups niA, rVA, and VA are called post-transition metals. 

It is often useful to refer to whole blocks of elements on the periodic table. The elements in groups 1, 2, and 13 through 18 (the A groups) are sometimes called the representative elements. They are also called the main-group elements. The elements in groups 3 through 12 (the B groups) are often called the transition metals. The 28 elements at the bottom of the table are called inner transition metals. 

Representative elements The elements in groups 1, 2, and 13 through 18 (the A groups) on the periodic table also called main-group elements. 

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