Example 1

Example 1

EXAMPLE Predicting Types and Strengths of Attractions Between Particles:  

For each of the following substances, write the name for the type of particle that forms its basic structure and the name of the primary type of attraction between these particles. From each pair of substances, choose the one that you expect to have the stronger interparticle attractions.

a. ethylene, C2H4 (used to make polyethylene plastic)

propylene, C3H6  (used to make polypropylene plastics for toys and other uses)

b. sodium fluoride, NaF  (used to fluoridate municipal water)

nitrogen trifluoride, NF3  (oxidizer for high-energy fuels)

c. ammonia, NH3  (used to make fertilizers)

methane, CH4  (major component in natural gas)

d. methanol, CH3OH  (used as a solvent and a fuel)

potassium, K  (used with sodium in heat-exchange alloys)

e. 1-propanol, CH3CH2CH2OH  (solvent for waxes and vegetable oils)

methanol, CH3OH  (used to make formaldehyde for embalming fluids)

f. carbon in the diamond form, C(dia)  (used for windows in space probes)

fluorine, F2  (used to make compounds added to toothpaste)


a. Ethylene, C2H4 and propylene, C3H6 are both hydrocarbons, so they are nonpolar molecular substances with London forces operating between the molecules. Larger molecules exert stronger London forces, so the attractions between C3H6 molecules are stronger than those between C2H4 molecules.

b. Sodium is a metal, and fluorine is a nonmetal, so we predict that NaF is an ionic compound, held together with ionic bonds. The compound NF3 is a molecular substance with an asymmetrical distribution of polar bonds, so it is a polar molecular compound with dipole-dipole attractions between the molecules (enhanced by London forces). Ionic bonds are stronger than dipole-dipole attractions, so NaF has the stronger attractions between particles.

c. The formula NH3 represents a molecular, substance possessing N-H bonds, so it is a polar molecular compound with hydrogen bonds between the molecules (enhanced by London forces). Methane is a hydrocarbon, so it is a nonpolar molecular substance with London forces operating between the particles. For molecules of about the same size, hydrogen bonds are stronger than London forces, so NH3 has the stronger interparticle attractions.


d. Methanol is an alcohol, and alcohols are polar molecular compounds with hydrogen bonds that link the molecules together (enhanced by London forces). Potassium atoms are held together by metallic bonds. Metallic bonds are stronger than hydrogen bonds, so potassium has the stronger interparticle attractions.

e. Both substances are alcohols, which are polar molecular compounds. The primary attractions between alcohol molecules are hydrogen bonds, but London forces also play a part. The larger 1-propanol molecules have stronger London forces between them.

f. Carbon and fluorine are both nonmetallic elements. Carbon in the diamond form is composed of atoms held together by covalent bonds. Fluorine, F2, is composed of molecules held together by London forces. The covalent bonds in a diamond are much stronger than the London forces between F2 molecules.

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