Silicon elemental boron

The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. 

Boron (like silicon) invariably occurs in nature as 0X0 compounds and is never found as the element or even directly bonded to any other element than oxygen. The structural chemistry of B-O compounds is characterized by an extraordinary complexity and diversity which rivals those of the borides (p. 145) and boranes (p. 151). In addition, vast numbers of predominantly organic compounds containing B-O are known. 

Hydrides are an important group of precursors that are used to deposit single elements such as boron or silicon. As described in Ch. 4, they are also used in conjunction with metallo-organics to form III-V and II-VI semiconductor compounds as shown in the following examples ]... 

Borasiloxane 92 with boron and silicon atoms at alternate corners and the general formula B4Si40io for the central cage is composed of two dib-oratetrasiloxane rings, that are joined by two Si-O-Si bridges [129]. Unlike the related and extensively studied silasesquioxanes 93 (Fig. 25), in which the silicon atoms can be substituted by various combinations of group 13 and 15 elements [137], this molecule contains alternately three-coordinate boron and four-coordinate silicon corner sites. 

Somewhat disappointingly, the values of AHf [A(g)] of some first-and second-row elements A (notably boron and silicon) are not precisely known because of a variety of experimental difficulties. However, well-established precise heats of formation of BF3 [69] and SiF4 [70] are... 

The essential microelements are only required in trace amounts (see also p.2). This group includes iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), cobalt (Co), chromium (Cr), selenium (Se), and molybdenum (Mo). Fluorine (F) is not essential for life, but does promote healthy bones and teeth. It is still a matter of controversy whether vanadium, nickel, tin, boron, and silicon also belong to the essential trace elements. 

Other elements such as boron and silicon can be found in fuel and oil system deposits. They can originate from the following sources ... 

References Stock, Hydrides of Boron and Silicon (1933) Paneth, Radio Elements as Indicators and Other Selected Topics in Inorganic Chemistry (1928) Stewart, Recent Advances in Physical and Inorganic Chemistry, 6th ed. Chap. XVI (1930). 

Metalloid (semi-metal) Any of the class of chemical elements intermediate in properties between metals and non-metals, for example boron and silicon. 

Borosilicate glass and ceramics are inert materials and have great chemical stability the weak point about glass, however, is its fragility. Glass can be used for both organics and inorganics, but one should be mindful of the fact that it is a potential source of boron and silicon and cannot be used if these elements are to be determined. 

Boron and silicon compounds are well established in organic synthesis and a bewildering array of reactions involving these elements is reported every year. The small number of pages traditionally allotted to these elements in one-volume textbooks now fails to emphasize their importance and their wide range of uses. 

Trichlorosilane is used in the production of semiconductor grade silicon. By repeated distillation the content of boron or phosphorus impurities can be reduced to <0.1 ppb. Elemental silicon is obtained by reduction with hydrogen at high temperatures according to the idealized equation 6. 

Here in Group III was a gap between calcium and titanium. Since it occurred under boron, the missing element must resemble boron. This was his eka-boron which he predicted. There was another gap in the same group under aluminum. This element must resemble aluminum, so he called it eka-aluminum. And finally he found another vacant space between arsenic and eka-aluminum, which appeared in the fourth group. Since its position was below the element silicon, he called it eka-silicon. Thus he predicted three undiscovered elements and left it to his chemical contemporaries to verify his prophecies. Not such remarkable guesses after all—at least not to the genius Mendel eff ... 

The atomic heats are therefore 5-83, 5-74 and 6-26 over the three ranges of temperature (1), (2), (3). There is a slight deviation from Dulong and Petit s law 9 at the lower temperatures, in the same sense as that met with in the case of the elements carbon, boron and silicon. But although phosphorus has a relatively low atomic weight, it also has a low melting-point, and the atomic heat as usual assumes the normal value at temperatures near the melting-point. 

Metalloid. An element of metallic appearance but poor electric conductivity, such as boron or silicon or germanium. Chemically, the metalloids are not so strongly electropositive as the metals and tend principally toward covalent bonding. 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, silicon, and sulfur are not included these are of interest, however, because of their stability at high temperatures. A large number of ternary compounds, including numerous oxyhalides, and more complicated compounds have been synthesized and characterized. These include many intermediate (nonstoicliiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teflurates, tellurites, selenides, and tellurides. 

---