CK-12 Chemistry - Basic Answer Key Chapter 8: Ionic and Metallic Bonding 8.1 Ions Practice 8.1 Write the ground state configuration for the metal calcium, and predict the ion form it must become to be isoelectric with the nearest noble gas. Answer: Ca: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 or [Ar]4s 2 The nearest noble gas to calcium is [Ar]. So calcium will typically lose two electrons to become isoelectric with [Ar]. Practice 8.2 Write the ground state configuration for the nonmetal sulfur, and predict the ion form it must become to be isoelectric with the nearest noble gas. Answer: S: 1s 2 2s 2 2p 6 3s 2 3p 4 or [Ne]3s 2 3p 4 The nearest noble gas to sulfur is [Ar], so sulfur will typically gain two electrons to become [Ne] 3s 2 3p 6 which is isoelectric with [Ar] Lesson Review Questions Questions 1. Draw electron dot diagrams for one metal and one nonmetal from the periodic table. 2. Predict which of the following will likely become a cation or an anion. a. Ca b. Na c. F d. Br e. S 3. Write the ground state configuration for the following elements and predict the ion form it must become to be isoelectric with the nearest noble gas. a. Be 1
b. Mg c. O d. Al 4. What has to happen to make Li ---> Li+ 5. What would be the configuration for Mg-. Use the octet rule to explain why this is not likely to be a very stable ion. 6. What would be the electron configuration for F+? Use the octet rule to explain why this is not likely to be a very stable ion. 7. Element X has 16 electrons. a. Write the configuration for element X. b. How many electrons is this element away from having a complete octet? c. Make a prediction about the ion this element might form in an ionic compound. 8. Element Z has 12 electrons. a. Write the configuration for element X. b. How many electrons is this element away from having a complete octet? c. Make a prediction about the ion this element might form in an ionic compound. 9. Write the ground state configuration for the following elements. Then show how the element ionizes to become isoelectric with the nearest noble gas. Example: Mg [1s 2 2s 2 2p 6 3s 2 ] a. Na b. Ca c. N d. Br e. Al f. Se Mg Mg 2+ + 2e - [Ne] 2s 2 [Ne] 2+ g. Br Br + e- Br - [Ne]3s 2 3p 5 [Ar] - h. Se 2
Se + 2e- Se 2- [Ar]4s23d 10 4p 4 [Kr] 2- Answers: 1. Electron dots are used to denote valence electrons for a given chemical species. For example, the metal Aluminum has three valence electrons and would have a dot diagram of. The nonmetal nitrogen, has six valence electrons and would have the following dot diagram: 2. Answers: a. cation b. cation c. anion d. anion e. anion 3. Answers: a. 1s 2 2s 2 - The ion it will form is Be 2+, isoelectric with [He] b. 1s 2 2s 2 2p 6 3s 2 - The ion it will form is Mg 2+, isoelectric with [Ne] c. 1s 2 2s 2 2p 4 - The ion it will form is O 2-, isoelectric with [Ne] d. 1s 2 2s 2 2p 6 3s 2 3p 1 - The ion it will become is Al 3+, isoelectric with [Ne] 4. Lithium must lose one electron. 5. This is not likely, since magnesium is a metal and will likely become a cation when it combines with other chemical species. To become Mg -,it would need to gain an electron to have the configuration of [Ne] 3s 2 3p 1. This ionic configuration does not fulfill the octet rule. 6. This configuration would be [He]2s 2 2p 4 7. Answers: a. [Ne]3s 2 3p 4 b. 2 c. To become isoelectric with the nearest noble gas, [Ar], element X would need to gain 2 electrons, and would therefore take the form X 2-. 8. Answers: a. [Ne]3s 2 b. It would need to either gain 6 electrons to become isoelectric with [Ar] or lose 2 electrons to become isoelectric with [Ne], which is the more plausible scenario. c. The ion of this element would likely become X 2+ 9. Answers: a. Na [Ne]3s 1 Na Na + + e - [Ne] 3s 1 [Ne] + b. Ca [Ar]4s 2 3
Ca Ca 2+ + 2e - [Ar] 4s 2 [Ar] 2+ c. N [He] 2s2, 2p3 N + 3e- à N3- [He] 2s2 2p6 or [Ne] d. Br Br + e- Br - [Ne]3s 2 3p 5 [Ar] - e. Al [Ne] 3s2 3p1 Al à Al3+ + 3e- f. Se Se + 2e- Se 2- [Ar]4s23d 10 4p 4 [Kr] 2-8.2 Ionic Bonds and Ionic Compounds Check Your Understanding 1. Define ion and give examples of ions that commonly form. Answers: Ions are formed from elements by either gaining or losing electrons to obtain a noble gas configuration. Typical cations are Na +, Mg 2+, and Al 3+. Typical anions are Cl - and O 2-. 2. Draw the electron dot diagram for the following elements: o Calcium Ca o Oxygen : O : Lesson Review Questions 4
Questions 1. How do the electrons from two atoms interact in an ionic bond? 2. Predict the formulas for the ionic compounds formed when each of the metals in the Table below reacts with each nonmetal. Calcium Sodium Aluminum Oxygen Sulfur Chlorine 3. What is dissolution? 4. If sodium chloride is placed in water, it will completely dissociate into its ionic components, described by the dissociation equation: NaCl(aq) ---> Na+ (aq) + Cl-(aq) [the (aq) signifies that the salt is soluble will dissociate] Write a similar dissociation equation for the dissociation of the ionic compound calcium chloride? 5. Which physical properties of ionic compounds can be attributed to the crystal lattice structure? 6. How does lattice energy relate to the strength of an ionic compound? 7. True or false: The high melting points of ionic solids suggest that ionic bonds are fairly weak 8. Using table 8.1 as a reference, what trend can be recognized between lattice energy and the characteristics of the ions which comprise the compound. For example, NaF, NaCl, NaBr, NaI have lattice energies (kj/mol) of 910, 788, 732, and 682, respectively. What is different between the anions that may be causing such differences? Answers: 1. Ionic bonds are electrostatic attractions between two oppositely charged ions. Ions can be formed and then bonded when metal ions donate their valence electrons to nonmetal atoms. 2. Answer: Oxygen Sulfur Chlorine Calcium CaO CaS CaCl 2 Sodium Na 2 O Na 2 S NaCl 5
Aluminum Al 2 O 3 Al 2 S 3 AlCl 3 3. Dissolution is a process in which water interacts with the ions in a crystal lattice, causing the lattice to break apart. 4. CaCl2 (s) à Ca2+ (aq) + 2 Cl- (aq) 5. Ionic compounds are composed of extremely large numbers of cations and anions. Each cation is attracted by all of the anions but are repelled by other cations. Ions form a three-dimensional structure known as a crystal lattice in order to maximize the number of attractive interactions and minimize the repulsive ones. 6. Lattice energy is the amount of energy needed to completely pull apart an ionic substance into isolated ions and can be calculated based on measured energy changes to determine the relative strength of an ionic bond. 7. True 8. The lattice energy decreases as the size of the anion increases. A larger anion increases the distance between the cation and the anion in the crystal. 8.3 Metals and Metallic Bonds Check Your Understanding 1. Identify the ions in the following compounds a. NaCl Na + and Cl - b. BaSO 4 Ba 2+ 2- and SO 4 c. K 2 O K + and O 2-2. How many valence electrons do most metals exhibit? Answer: One to three Lesson Review Questions 1. Define the following properties of metals a. Malleability b. Ductility c. Toughness d. Luster 2. In metal solids, the electrons form a shared sea of electrons. 3. What is corrosion as it applies to metals? 4. In general, what can be said of the melting points of metals? 5. Define a metallic bond. 6
6. What is the relationship between the electron arrangement in metals and metals physical properties? 7. What atomic properties distinguish precious metals from metals in general? 8. Why are rare metals so valuable? 9. How are alloys formed? Answers: 1. a. The ability to be stamped, pressed or rolled into thin sheets b. The ability to be stretched, bent or twisted without breaking c. The ability of a material to withstand shock and to be deformed without rupturing d. Shiny 2. Valence electrons 3. Corrosion is the gradual degradation of a material due to its exposure to the environment. 4. Metals have a wide range of melting points, but most are high. 5. A metallic bond is the attraction of the stationary metal cations to the surrounding mobile electrons 6. Pure metals generally have a few valence electrons that tend to be fairly easy to remove due to metals low ionization energy and electronegativity values. This allows them to combine with nonmetals to create ionic compounds by transferring their valence electrons to complete their valence shells and achieve noble gas configurations. 7. Compared to other metals, precious metals tend to have relatively high ionization energies and electronegativity values. They are referred to as precious due to their scarcity and their ability to remain pure over time. 8. Rare metals are valuable because of their importance in a variety of industrial processes and use in modern technology. Despite their name, they are relatively abundant in nature but often times, difficult to extract. 9. Melting down and combining pure elemental forms to make a mixture of reactants create alloys. 7