Properties of Main-Group Elements

Elements in a periodic table group have similar properties, but not the same properties. Some properties, as already illustrated for atomic radii and reactivity, increase or decrease in a predictable fashion from top to bottom of a periodic group. 

The Group 2A elements (Be, Mg, Ga, Sr, Ba, and Ra) are called the alkaline earth metals. Compared with the alkali metals, the alkaline earth metals are harder, are more dense, and melt at higher temperatures. These elements form cations with a + 2 chaise. Because the valence electrons of alkaline earths are held more tightly, they are less reactive than their alkali metal neighbors. All the alkaline earth metals react with oxygen to form an oxide MO, where M is the alkaline earth. 

See an animation of Ion Formation at http //brookscole.com/chemistrv/ ioesten4 

Recall that the only other diatomic elements are Hj. N, and Oj. 

How many valence electrons are in each of the following atoms  

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Table 1. Calculated properties of main group elements...

TABLE II Some Physical and Atomic Properties of Main Group Elements, Groups 13-16 (IIIA-VIA)... 

The arrangement of the elements considering their properties as a function of their atomic number established in the Periodic Table permits us to classify them into two large groups The Main Group Elements, i.e. the alkaline, alkaline earth, and post-transition elements, and the Transition Metals. Table 4.1 summarizes selected properties of Main Group Elements. 

The properties of main-group elements can generally be predicted from their position in the periodic table. The properties of the elements in the middle of the table, known as transition elements, are less predictable. 

A plot of density versus element is given below (table only shows a few elements used in the plot. Density clearly is a periodic property for these two periods of main group elements. It rises, falls a bit, rises again, and falls back to the axis, in both cases. 

The oxides of main-group elements show periodic trends in properties. Oxides of metals tend to be ionic and to form basic solutions in water. Oxides of nonmetals are molecular and the anhydrides of acids. 

FIGURE 14.6 Formulas, acid-base properties, and the covalent-ionic character of the oxides of main-group elements in their highest oxidation states. Basic oxides are shown in blue, acidic oxides are shown in red, and amphoteric oxides are shown in violet. 

The change in the basic and acidic properties here shown for the oxides of main group elements which have the highest oxidation state number. The oxides in the blue colored regions are basic (metallic) oxides and the oxides in the red colored regions are acidic (nonmetallic) oxides. The oxides in both blue and red colored regions are amphoteric oxides (the oxides of amphoteric metals). 

Locate the different families of main-group elements on the periodic table, describe their characteristic properties, and relate their properties to their electron configurations. 

Boron (B) heads the third family of main-group elements, but its properties are not representative, as the Group 3A(13) Family Portrait shows. Metallic aluminum (Al) is more typical of the group, but its great abundance and importance contrast with the rareness of gallium (Ga), indium (In), and thallium (Tl). 

The atomic properties of the transition elements contrast in several ways with those of a comparable set of main-group elements (Section 8.4). 

Write electron configurations of transition metal atoms and ions compare periodic trends in atomic properties of transition elements with those of main-group elements explain why transition elements have multiple oxidation states, how their metallic behavior (type of bonding and oxide acidity) changes with oxidation state, and why many of their compounds are colored and paramagnetic ( 22.1) (SP 22.1) (EPS 22.1 -22.17)... 

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