Which of the following are ionic compounds? A. KCl B. NaOH C. CH 4 D. CO 2 E. CaO. Disassociation reaction: 3.1 Ionic and Molecular Compounds

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1 3.1 Ionic and Molecular Compounds 10:21 AM Terms for this section: Electrolyte Nonelectrolyte Strong Electrolyte Weak Electrolyte Ionic Compound (salt) Molecular Compound Binary Compounds Ionization/Disassociation Which of the following are ionic compounds? A. KCl B. NaOH C. CH 4 D. CO 2 E. CaO Disassociation reaction: Chapter 3 Page 1

2 Properties of Ionic vs. Molecular Compounds Ionic Compound Molecular Compound Crystalline solid Solid, Liquid, or Gas Hard, brittle solid Soft Solid Very High Melting Point Low Melting Point Very High Boiling Point Low Boiling Point High Density Low Density Strong Electrolyte Weak or Nonelectrolyte Conductivity in molten form Poor conductivity Chapter 3 Page 2

3 3.2 Monatomic and Polyatomic Ions 10:24 AM Terms in this Section: Monatomic Ion Polyatomic ion Oxoanion Common Monatomic Ions: -Oxide -Sodium -Nitride -Aluminum -Magnesium -Chloride -Potassium -Flouride Polyatomic Ions and Oxoanions Polyatomic ions are ions that contain more than a single atom, the most common are the Oxoanions which contain oxygen bound to other elements. Naming Oxoanions Single Oxoanion - ends in -ate (such as Borate) Two Ions and Oxoanions in sequence No Oxygen - ends in -ide (such as Chloride) Chapter 3 Page 3

4 Two Ions and Oxoanions in sequence No Oxygen - ends in -ide (such as Chloride) Most Numbers of Oxygen - ends in -ate Three Ions and Oxoanions in sequence No Oxygens - ends in -ide Middle Numbers of Oxygen - ends in -ite (such as Sulfite) Most Numbers of Oxygen - ends in -ate Some compounds have a total of five in the sequence. No Oxygens - ends in -ide Most Oxygens - prefix of per- and suffix of -ate Next Most - ends in -ate Next to Least - ends in -ite Least Oxygens - prefix of hypo- and suffix of -ite Learn the common Polyatomic Ions in Table 3.4! Chapter 3 Page 4

5 3.3 Formulas for Ionic Compounds 10:24 AM Formula Unit vs. Chemical Formula Ionic Compounds do not exist as discrete molecules and therefore do not have discrete chemical formulas. You must report the smallest unit value of the crystal lattice that balances to a net charge of zero. Problems: Write the formula for the following- A. Calcium perchlorate B. Sodium bromide C. Lithium hypochlorite D. Potassium Cyanide Chapter 3 Page 5

6 Chapter 3 Page 6

7 Chapter 3 Page Naming Ionic Compounds 10:24 AM The names of ionic compounds are usually the metal followed by the nonmetal name. In the case of polyatomic ions, you use the appropriate name for the form present. NaO = Sodium Oxide NaCl = Sodium Chloride Li 3 PO 4 = Lithium Phosphate Mg(ClO) 2 = Magnesium Hypochlorite Note you do not need to denote the number of each atom present in the formula unit, since it can be deduced from the type of ion. Try the following: A. Ca(NO 3 ) 2 = B. K 2 O =

8 Chapter 3 Page 8 C. LiN = D. Rb 4 SiO 4 = It isn't always so nice and neat, once you get into the transition metals and the metals of Groups IIIA-VIA, many of these exhibit multiple charge states and therefore can have multiple formula units. For example, there is both a CuCl and CuCl 2 How can this be, this would mean that sometimes Copper is a +1 cation and sometimes it is a +2 cation exactly. We have to have a way to distinguish between these two types of

9 Chapter 3 Page 9 compounds. There are a few ways to do this. The preferred way is simply to designate the charge in the name with roman numerals. Such as CuCl = Copper (I) Chloride CuCl 2 = Copper (II) Chloride There is another way, an older but still used methodology, where the lower charge ends the metal is -ous and the higher charge ends the metal in -ic. Therefore you would get CuCl = Copper (I) Chloride = Cuprous Chloride CuCl 2 = Copper (II) Chloride = Cupric Chloride This gets even weirder because the names of the metals don't always match the element. FeCl 2 = Iron (II) Chloride = Ferrous Chloride FeCl 3 = Iron (III) Chloride = Ferric Chloride SnO = Tin (II) Oxide = Stannous Oxide PROBLEMS

10 Chapter 3 Page 10 A. CrO = B. Co(NO 2 ) 3 = C. (Hg 2 ) 3 (PO4) 2 = I advise sticking to the numbering system since it is valid and easier to make sense of. The other system is used and you should be aware of it, but is outdated. Know Figure 3.24

11 Chapter 3 Page Naming and Writing Formulas for Molecular Compounds 10:24 AM The names of molecular compounds differ because there are a finite number of atoms present in a molecule (in contrast to the simplest ratio of ionic compounds). Therefore we need to explicitly state the number of atoms for each element present. This is done as follows for binary molecular compounds. 1. The name starts with the element that is first in the molecular formula. 2. If there is more than one of that element present a Greek prefix (Table 3.9) is added to denote the number. 3. The second element is added as a root with the suffix -ide and if there is more than one, an appropriate Greek prefix of magnitude. CCl 4 = Carbon Tetrachloride SO 3 = Sulfur Trioxide (not to be confused with SO 3-2 ) Name the Following: 1. P 4 O 6 = 2. N 2 O 5 = There are trivial exceptions such as water, ammonia and hydrogen peroxide, but you should strive to systematic.

12 Chapter 3 Page Acids and Bases 10:25 AM Acid = Any substance that provides hydrogen ions (H + ) when dissolved in water. These are typically molecular compounds that ionize, a type of disassociation, in water. The following is a typical ionization reaction. This differs from the breakdown of an ionic compound because the process is not complete, rather on part of the substance ionizes (which we will learn about in equilibria) HCl (g) + H 2 O (l) ----> H 3 O + (aq) + Cl - (aq) So what is H 3 O + This is the hydronium ion and represents the association of the freed hydrogen ion with water. Acids are typically produced between hydrogen and element on the right of the periodic table (halogens being notable), though there are exceptions to this. Work through tables 3.10 and 3.11 to see if you can work out the naming rules for binary acids. Base = any compound that dissolved in water reacts with an acid to form water. This may be through the release of OH -, or through the production of OH -. NaOH NH 3

13 Chapter 3 Page 13 Review Problems 10:26 AM Try to do the following, without your notes or book at first. These types of problems will be on the exam. Given the following formulas, please name the compounds. 1. Na 3 As : 2. MgO : 3. Ba 3 (BO3) 2 : 4. NH 4 Cl : 5. K 2 Cr 2 O 7 : Write the formula units for the following compounds 1. Barium Phosphate: 2. Iron (III) Chloride: 3. Lithium Nitride: 4.