Molecular formula, covalent bonds

The element phosphorus forms a variety of allotropic forms in the solid state. In the chemistry stockroom, you are likely to find red phosphorus and possibly white phosphorus (Figure B). As you can see, white phosphorus has the molecular formula P4, whereas red phosphorus might be represented as Px, where x is a very large number. The difference in properties between the two allotropes reflects the difference in their bonding patterns, molecular versus network covalent ... 

Stereoisomers, on the other hand, are compounds with the same molecular formula, and the same sequence of covalently bonded atoms, but with a different spatial orientation. Two major classes of stereoisomers are recognized, conformational isomers and configurational isomers. 

The element carbon (symbol C) is almost always found in nature covalently bonded to other carbon atoms or to a variety of other elements (most commonly H, O, and N). Due to the presence of carbon-containing compounds in all living things, the chemistry of carbon compounds is known as organic chemistry. Most high explosives are organic compounds. TNT (trinitrotoluene), for example, consists of C, H, N, and O atoms, with a molecular formula of C yH 5N P e. We will encounter other organic compounds in our study of fuels and binders in pyrotechnic mixtures. 

Molecular formulas merely include the kinds of atoms and the number of each in a molecule (as C4H , for butane). Structural formulas show the arrangement of atoms in a molecule (see Fig. 1-1). When unshared electrons are included, the latter are called Lewis (electron-dot) structures [see Fig. 1-1(/)]. Covalences of the common elements—the numbers of covalent bonds they usually form—are given in Table 1-1 these help us to write Lewis structures. Multicovalent elements such as C, O. and N may have multiple bonds, as shown in Table 1-2. In condensed structural formulas all H s and branched groups are written immediately after the C atom to which they are attached. Thus the condensed formula for isobutane [Fig. l-l(f>)) is CH,CH(CH,)... 

Elemental Composition, Molecular Formula, and Molar Mass Electron Shells of Elements Present in Organic Compounds Covalent Bonding... 

These three hydrocarbons all have the same molecular formula. We can see their different structural features by highlighting the carbon framework in two dimensions. Easy-to-draw stick structures that use lines for all carbon—carbon covalent bonds can also be used. 

The first thing you must be able to do in order to predict molecular shapes is to draw an electron-dot formula, so we ll tackle that subject first Including H, there are 16 active nonmetals for which you should know the numbers of valence electrons in the uncombined atoms Except for H (which has only one s electron), these elements are all found to the right of the diagonal in the p block of the periodic table (see inside front cover) Each atom has two v electrons in its valence shell, the number ofp electrons is different for different atoms (Basically, we are uninterested in metals here, metals rarely form predominantly covalent bonds, but tend to form ionic bonds ignore the noble gases, with an already filled s-yi6 unreactive )... 

Sometimes it is possible to write more than one structural formula to represent a molecular formula. The structural formula of a compound shows how the atoms are joined together by the covalent bonds. For example, there are two different compounds with the molecular formula C4H10. The structural formulae of these two substances along with their names and physical properties are shown in Figure 14.4. 

The nomenclature for molecular compounds is much less complicated than for ionic compounds. Molecular compounds are formed from covalently bonded nonmetallic elements. The formula for a molecule represents a stable unit of atoms, unlike a formula for an ionic compound, which only represents the simplest whole number ratio of ions. As a result, molecular formulas cannot be simplified like formulas for ionic compounds. An example would... 

Molecular Formulas Molecular formulas indicate the total number of atoms of each element that are present in a covalently bonded molecule. An example is CH4, which indicates that there is one carbon atom and four hydrogen atoms in this covalently bonded molecule of methane. 

By this point in this book you should have come across a few familiar acids and bases. Either you recognized the molecular formula of an acid or a base or you saw the name of a familiar acid or base. Acids and bases can be defined in a number of ways, as you will see shortly. It s a good idea to see how acids and bases are named before you focus on the differences between them. You will see that the names do not follow the same rules used for other covalently bonded substances. 

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