Covalent compounds molecular hydrogen

Does the formula contain a metal (not hydrogen) If there s no metal, you re naming a molecular (covalent) compound, so you need to use the prefixes in Table 6-2. Be sure to change the ending of the second element to -ide. If there is a metal, then you re dealing with an ionic compound, so proceed to Question 3. 

Alkanes are covalent compounds in an homologous series which has the general molecular formula C H2 +2. Thus for methane, which is the simplest of the series, n— (there is only one carbon atom), so there are (2x l) + 2 = 4 hydrogen atoms hence methane s formula is CH4. 

Common names of some molecular compounds How frequently have you drunk an icy, cold glass of dihydrogen monoxide Quite frequently, hut you probably didn t call it that. You called it by its more common name, which is water. Remember from Chapter 8 that many ionic compounds have common names in addition to their scientific ones. Baking soda is sodium hydrogen carbonate and common table salt is sodium chloride. Many covalent compounds also have both common and scientific names. 

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 be hydrogen peroxide, H O. Although the formula could be reduced to HO, this would be inappropriate because 11,0, is a molecule. Changing the structure to HO would change the chemical composition. 

Since the immediate electronic environment of the deuterium nucleus in most compounds is relatively simple, deuterium quadrupole coupling constants show very systematic variations with molecular structure. In covalent compounds, except those with hydrogen bonds or multicentered bonds (as in many boron deuterides), deuterium is bonded to only one atom. The bonding electrons have essentially cylindrical symmetry, and the only asymmetry in the electronic environment of deuterium comes from indirectly bonded atoms. Therefore, in many cases, 17 is very small 0.1). 

The subscripts in the formula of a compound give the ratio of the number of atoms of each element to the number of atoms of each other element in the formula. The collection of atoms written to represent the compound is defined as one formula imit. That is, the formula unit of ammonium sulfide, (NH4)2S, contains two atoms of nitrogen, eight atoms of hydrogen, and one atom of sulfur. The term formula mass (sometimes called formula weight) refers to the sum of the atomic masses of every atom (not merely every element) in a formula unit. There are several names for formula masses corresponding to different kinds of formulas. For uncombined atoms, the formula mass is the atomic mass. For covalent compounds, which consist of molecules, the formula mass can be called the molecular mass. For ionic compounds, there is no special name for formula mass. These terms are summarized in Table 4-1. 

The role of water in the solution process deserves special attention. It is often referred to as the "universal solvent" because of the large number of ionic and polar covalent compounds that are at least partially soluble in water. It is the principal biological solvent. These characteristics are a direct consequence of the molecular geometry and structure of water and its ability to undergo hydrogen bonding. 

We have seen that carbon forms four covalent bonds and hydrogen forms only one covalent bond (Section 1.4). This means that there is only one possible structure for an alkane with molecular formula CH4 (methane) and only one structure for an alkane with molecular formula C2H6 (ethane). We examined the structures of these compounds in Section 1.7. There is also only one possible stracture for an alkane with molecular formula CsHg (propane). 

LiH (lithium hydride) ionic compound BeH2 (beryllium hydride) covalent compound B2H6 (diborane, you aren t expected to know that name) molecular compound CH4 (methane, do you know that one ) molecular compound NH3 (ammonia, you should know that one) molecular compound H2O (water, if you didn t know that one, you should be ashamed) molecular compound HF (hydrogen fluoride) molecular compound. LiH and BeH2 are solids, B2H6, CH4, NH3, and HF are gases, and H2O is a liquid. 

Many of the reactions of interest in the course you are taking occur between compounds or elements dissolved in water. Ionic compounds and some polar covalent compounds break apart (dissociate) into ions when they are dissolved in water. Thus, a water solution of sodium hydroxide (NaOH), an ionic compound, does not contain molecules of NaOH but, rather, contains equal numbers of sodium ions (Na ) and hydroxide ions (OH ). Covalently bonded hydrogen chloride, HCl, dissolves readily in water to form and Cr ions. Equations for reactions between substances that form ions in solution can be written in several ways. For example. Equation 5.22 contains three substances that form ions, HCl, NaOH, and NaCl. Equation 5.22 is written in the form of a molecular equation in which each compound is represented by its formula. This same reaction, when represented by a total ionic equation, becomes... 

---