Binary hydrides group

Hydrogen combines with many elements to form binary hydrides MH (or M H ). All the main-group elements except the noble gases and perhaps indium and thallium form hydrides, as do all the lanthanoids and actinoids that have been studied. Hydrides are also formed by the more electropositive transition elements, notably Sc, Y, La, Ac Ti, Zr, Hf and to a lesser... 

Valence and oxidation state are directly related to the valence-shell electron configuration of a group. Binary hydrides are classified as saline, metallic, or molecular. Oxides of metals tend to be ionic and to form basic solutions in water. Oxides of nonmetals are molecular and many are the anhydrides of acids. 

You can see the effect of hydrogen bonding clearly in the boiling point data of the binary hydrides of Groups 14 to 17 (IVA to VIIA), shown in Figure 4.16. In Group 14, the trend in boiling point is as expected. 

Some binary hydrides (e.g. those of Groups 16 and 17) behave as acids in aqueous solution, but the majority of acids are oxoacids derived from acidic oxides. This discussion is restricted to the factors influencing the production of acids or bases when oxides dissolve in water. An oxide can be acidic, amphoteric i.e. acidic or basic depending upon conditions) or basic. 

The periodic trends in main-group elements become apparent when we compare the binary compounds they form with one specific element. All the main-group elements, with the exception of the noble gases and, possibly, indium and thallium, form binary compounds with hydrogen, so these hydrides can be examined to look for periodic trends. We meet the binary hydrides several times in this chapter and the next, so, at this stage, we confine the discussion to a brief survey and see how their properties reveal periodic behavior. 

Boiling Points of the Covalent Binary Hydrides of Groups 4A, 5A, 6A, and 7A... 

The binary hydrides are compounds that contain hydrogen and just one other element. Formulas and melting points of the simplest hydrides of the main-group elements are listed in Figure 14.2. Binary hydrides can be classified as ionic, covalent, or metallic. 

Apart from the binary hydrides of Groups 16 and 17, Lowry/ Brpnsted acids in aqueous solution are nearly all oxoacids, i.e. substances containing O-H bonds which ionise in aqueous solution to give oxo-anions and H+(aq) (or H30+). Most oxoacids are molecular hydroxides E(OH) , such as B(OH)3, Ge(OH)4 and Te(OH)6, or oxohydroxides EOm(OH) . In addition, we have more complex species containing E-E bonds or E-O-E bridges. In EOm(OH) - for example, N02(0H), PO(OH)3, S02(0H)2,103(0H) - the m O atoms are held to E by bonds having at least some double bond character, via p -p or d -p overlap. Oxohydroxides may be seen as being derived from hydroxides by elimination of H20, and are favoured by elements E whose atoms form double bonds to O atoms. 

The binary hydrides (p. 67), borides (p. 148), carbides (p. 299), and nitrides (p. 418) of these metals have already been discussed and will not be described further except to note that, as with the analogous compounds of Group 4, they are hard, refractory and nonstoichiometric materials with high conductivities. The intriguing cryo-compound [V(N2)6] has been isolated by cocondensing V atoms and N2 molecules at... 

Write the formulas of the binary hydrides for the second-period elements (LiH to HF). Illustrate the change from ionic to covalent character of these compounds. Note that beryllium behaves differently from the rest of Group 2A metals (see p. 344). 

TABLE IV Characteristic Features of Binary Main Group and Transition Metal Hydrides ... 

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