Sodium ion is surrounded by six chloride ions and

This preview shows page 32 - 35 out of 55 pages.

sodium ion is surrounded by six chloride ions, and each chloride ion is surrounded by six sodium ions. Any ionic compound that has the same arrangement of cations and anions as NaCl is said to have the sodium chloride crystal structure. The ionic compounds in this category include AgF, AgCl, AgBr, and the oxides and sulfides of the alkaline earth metals, such as MgO, CaS, etc. The sodium chloride crystal structure is just one of many different possible arrangements of ions in solid ionic compounds. O BJECTIVE 31 100 Chapter 3 Chemical Compounds There are two tutorials on the textbook’s Web site that provide practice converting between names and formulas of cations and anions.
Image of page 32

Subscribe to view the full document.

3.5 Ionic Compounds 101 Figure 3.18 Sodium Chloride Structure O BJECTIVE 32 Polyatomic Ions When an electric current is run through a purified saltwater solution (brine), hydrogen gas, chlorine gas, and an ionic compound called sodium hydroxide, NaOH, form. The sodium hydroxide, commonly called caustic soda or lye, is a very important compound that is used in paper production, vegetable oil refining, and to make many different compounds, such as soap and rayon. Like sodium chloride, NaCl, sodium hydroxide, NaOH, contains a cation and an anion, but unlike the monatomic Cl anion in NaCl, the hydroxide ion, OH , in NaOH is a polyatomic ion , a charged collection of atoms held together by covalent bonds. To show the charge, Lewis structures of polyatomic ions are often enclosed in brackets, with the charge indicated at the top right. The Lewis structure for hydroxide is O H hydroxide Note in the Lewis structure above that the oxygen atom does not have its most common bonding pattern, two bonds and two lone pairs. The gain or loss of electrons in the formation of polyatomic ions leads to one or more atoms in the ions having a different number of bonds and lone pairs than is predicted on Table 3.1. The Lewis structure of the ammonium ion, NH 4 + , the only common polyatomic cation, is H H H H N + ammonium ion The ammonium ion can take the place of a monatomic cation in an ionic crystal structure. For example, the crystal structure of ammonium chloride, NH 4 Cl, which is found in fertilizers, is very similar to the crystal structure of cesium chloride, CsCl, which is used in brewing, mineral waters, and to make fluorescent screens. In each structure, the chloride ions form a cubic arrangement with chloride ions at the corners of each O BJECTIVE 33 Salt (sodium chloride) Ball-and-stick model Space-filling model Each sodium cation is surrounded by six anions. Each chloride anion is surrounded by six cations.
Image of page 33
cube. In cesium chloride, the cesium ions sit in the center of each cube, surrounded by eight chloride ions. Ammonium chloride has the same general structure as cesium chloride, with ammonium ions playing the same role in the NH 4 Cl structure as cesium ions play in CsCl. The key idea is that because of its overall positive charge, the polyatomic ammonium ion acts like the monatomic cesium ion, Cs + (Figure 3.19).
Image of page 34

Subscribe to view the full document.

Image of page 35
You've reached the end of this preview.
  • Fall '06
  • Mark
  • Atom, atoms, Chemical bond

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern