Covalent bond formation, conducting

Fig.6.1 depicts the Ebsworth diagram of N and P in acidic solution as well as N in basic solution. The top two elements in this group N and P are typical non-metals. The metallic character, which appears in the heavier elements, increases down the group, although the conductivity of solid Bi is not high. The typical oxidation numbers of all the members of the group are +3 and +5 but the stability of the +3 state in Bi is greater than the +S state (inert pair effect). The chemistry of N and P is dominated by covalent bond formation. On the other hand, ionic compounds of Bi(III) are the common bismuth compounds. The oxides of N and P are acidic in nature (except the neutral N2O and NO), the amphoteric nature becomes apparent in the oxides of the heavier elements. 

This chapter consists of two sections, one being a general discussion of the stable forms of the elements, whether they are metals or non-metals, and the reasons for the differences. The theory of the metallic bond is introduced, and related to the electrical conduction properties of the elements. The second section is devoted to a detailed description of the energetics of ionic bond formation. A discussion of the transition from ionic to covalent bonding in solids is also included. 

These, therefore, constitute the guidelines for finding superconductors or how to raise the superconducting temperature. Since Covalon conduction is a nucleus to superconductivity and covalent bond is a poor conductor at room temperature, a good conductor at room temperature implies a poor covalent bond and therefore will not be a superconductor or will be a poor superconductor at best at low temperature. Inasmuch as a good covalent bond can come from compound formation, good superconductors, particularly Type-II, shall be expected to come from intermetallic compounds or special type of ceramic oxides and nitrides. 

An additional requirement for high-temperature superconductivity is that such hypo-electronic atoms as La, Y, Ba, or Sr can interact with the hyperelectronic Cu atoms. This results in electron transfer from the Cu atoms to the hypoelectronic atoms, which leads to the formation of covalent bonds that resonate among the Y-Y and Y-Cu positions, conferring electronic conductivity on the substance. These two types of resonance caused by the combination of crest and trough metals couple with the phonons to yield superconductivity at relatively high temperatures. 

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