Oxides of the Group IVA Elements

The +4 oxides of the group IVA elements are generally acidic (as is C02) or amphoteric in character. As shown here for C02/ acidic oxides form oxyanions,... 

There is a much more extensive chemistry of the +4 oxides of the Group IVA elements than there is for the +2 oxides. In general, the E02 compounds are acidic or amphoteric oxides, and they show this characteristic by forming oxyanions. This type of behavior has also been illustrated for C02 by the reaction... 

The tetrahalides of the Group IVA elements hydrolyze to give the oxides, hydroxides, or hydrous oxides (E02, E(OH)4, or E02 2H20). Typical processes of this type are represented by the equations... 

Although the oxides of all the Group IVA elements are of some interest, the chemistry of Si02 is by far the most complex. Unlike C02 where double bonding results in the molecule having the structure... 

It follows from the foregoing discussion that, at least in principle, it should be possible to predict the local arrangement of ions in a crystal if the ratio rjr is known. To illustrate the general validity of this statement, consider the oxides of group IVA elements. The results are summarized in Table 3.1, and in all cases the observed structures are what one would predict based on the radius ratios. 

Lead forms various azides in its tetravalent state like the other IVA elements, but is the only member of the group to also form a normal azide in its lower (Pb ) oxidation state. 

There is also a pronounced tendency for the Group IIIA metals to form metal-metal bonds and bridged structures. The electron configuration ns2 np1 suggests the possible loss of one electron from the valence shell to leave the ns2 pair intact. The electron pair that remains in the valence shell is sometimes referred to as an inert pair, and a stable oxidation state that is less than the group number by two units is known as an inert pair effect. The fact that oxidation states of +2, +3, +4, and +5 occur for the elements in Groups IVA, VA, VIA, VIIA, respectively, shows that the effect is quite common. Thus, it will be seen that the Group IIIA metals other than aluminum have a tendency to form +1 compounds, especially thallium. 

Of the elements in Group IVA, carbon is a nonmetallic element that forms an acidic oxide, C02,... 

If a major breakthrough in nuclear synthesis were achieved, two elements that are hoped for are those with atomic numbers 114 and 164. both congeners of lead. Look at the extended periodic table in Chapter 14 and suggest properties (such as stable oxidation states) for these two elements How do you suppose their electroneguiivities will compare with those of the other Group IVA (14) elements ... 

In the case of manganese(I), with an electronic configuration of 3d , the four-electron donor group RCO— would meet the EAN rule. Indirect support to the suggestion of a small steady state concentration of this type of intermediate along the reaction profile comes from isolation of stable rj -coordinated acyl complexes of ruthenium(II) , of group IVA transition elements and of thorium , all in the highest oxidation state. Also > -acyl complexes of vanadium(I) ° and niobium(V) have been reported. Most of the molybdenum acyl complexes are of the type . 

Carbon, germanium, tin, lead, and silicon (atomic weight 28.086) comprise Group IVA of the Periodic Table of the elements. Silicon has three stable isotopes and three radioisotopes, and oxidation states of —4, + 2 and + 4. The element has a melting point of 1410 °C and a boiling point of 2680°C. 

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