Polar covalent substance

In polar covalent substances, the molecules have partial positive and negative charges because of the electronegativity differences between the atoms. The molecules are said to possess a dipole. 

Water, however, is a wonderful solvent for ionic-bonded substances such as salt. The secret to its success lies in the electric dipoles created by the polar covalent bonds between the hydrogen and oxygen atoms. In water, the polar bonds are asymmetric. The hydrogen side is positive the oxygen side is negative. One measure of the amount of charge separation in a molecule is its dielectric constant. Water has a dielectric constant that is considerably higher than that of any other common liquid. 

Many of the reactions that you will study occur in aqueous solution. Water is called the universal solvent, because it dissolves so many substances. It readily dissolves ionic compounds as well as polar covalent compounds, because of its polar nature. Ionic compounds that dissolve in water (dissociate) form electrolyte solutions, which conduct electrical current owing to the presence of ions. The ions can attract the polar water molecules and form a bound layer of water molecules around themselves. This process is called solvation. Refer to the Solutions and Periodicity chapter for an in-depth discussion of solvation. 

In this investigation, you will study the properties of five different types of solids non-polar covalent, polar covalent, ionic, network, and metallic. You will be asked to identify each substance as one of the five types. In some cases, this will involve making inferences and drawing on past knowledge and experience. In others, this may involve process-of-elimination. The emphasis is on the skills and understandings you use to make your decisions. Later, you will be able to assess the validity of your decisions. 

Solubility data are presented for practically all entries. Quantitative data are also given for some compounds at different temperatures. In general, ionic substances are soluble in water and other polar solvents while the non-polar, covalent compounds are more soluble in the non-polar solvents. In sparingly soluble, slightly soluble or practically insoluble salts, degree of solubility in water and occurrence of any precipitation process may be determined from the solubility product, Ksp, of the salt. The smaller the Ksp value, the less its solubility in water. 

Sanderson. R. T Polar Covalence-, Academic New York, 1983 Simple Inorganic Substances-,... 

In contrast with water and ammonia, carbon dioxide and tetrachloromethane (CCI4) have zero dipole moments. Molecules of both substances contain individual polar covalent bonds, but because of the symmetry of their structures, the individual bond polarities exactly cancel. 

It should be noted that self-ionisation is not an essential prerequisite for a satisfactory polar solvent. Liquids such as acetonitrile CH3CN or dimethylsulphoxide SO(CH3)2 appear not to ionise but they make very useful solvents for electrolytes as well as for polar molecular substances. As with H20, NH3, H2S04 etc., they owe their solvent powers to their polarity, leading to dipole-dipole interaction in the case of polar molecules as solutes and ion-dipole attraction in the case of electrolytes. There may in addition be considerable covalent bonding, via coordinate bond formation, in the case of cations. In solvents which do undergo appreciable self-ionisation, coordination often needs to be considered explicitly in discussing acid/base and other reactions and equilibria. 

Which substance has a polar covalent bond between its atoms ... 

The relationship between electronegativity and bond type is shown in Table 13.1. For identical atoms (electronegativity difference of zero) the electrons in the bond are shared equally and no polarity occurs. When two atoms with widely differing electronegativities interact, electron transfer usually occurs, producing ions—an ionic substance is formed. Intermediate cases give polar covalent bonds with unequal electron sharing. 

Compare the properties of an ionic substance, NaCl, with those of a nonpolar substance, I2, as shown in Figure 14. The differences in the properties of the substances are related to the differences in the types of forces that act within each substance. Because ionic, polar covalent, and nonpolar covalent substances are different in electron distribution, they are different in the types of attractive forces that they experience. 

Use the electronegativity values from Figure 4-la to determine if the bonds formed in the following substances will be ionic, polar covalent, or non-polar covalent. 

It is important to be able to tell whether a substance is ionic, nonpolar covalent, or polar covalent. You should review the discussion of bonding in Chapters 7 and 8. 

When a polar molecular substance, such as hydrogen chloride, is heated to convert it from liquid to gas, dipole-dipole attractions are broken. The molecules themselves remain unchanged. For example, when liquid FiCl is boiled, the dipole-dipole attractions between FiCl molecules are broken, but the covalent bonds between the hydrogen atoms and the chlorine atoms within the FiCl molecules are unaffected. 

If the substance is molecular, do the molecules contain polar covalent bonds ... 

Bromine monofluoride, BrF, a substance that liquefies at -20 °C, consists of polar Objective 20 molecules that are very similar to HCl molecules. Each BrF molecule consists of Objective 21 a bromine atom with a polar covalent bond to a fluorine atom, (a) Describe what... 

Water plays an active role in dissolving ionic compounds because it consists of polar molecules that are attracted to the ions. When an ionic compound dissolves in water, the ions dissociate from each other and become solvated by water molecules. Because the ions are free to move, their solutions conduct electricity. Water also dissolves many covalent substances with polar bonds. It interacts with some H-containing molecules so strongly it breaks their bonds and dissociates them into IT faq) ions and anions. In water, the ion is bonded to an H2O, forming HaO . ... 

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