Chapter 5. Table of Contents. Section 1 Simple Ions. Section 2 Ionic Bonding and Salts. Section 3 Names and Formulas of Ionic Compounds

Transcription

1 Ions and Ionic Compounds Table of Contents Section 1 Simple Ions Section 2 Ionic Bonding and Salts Section 3 Names and Formulas of Ionic Compounds

2 Section 1 Simple Ions Objectives Relate the electron configuration of an atom to its chemical reactivity. Determine an atom s number of valence electrons, and use the octet rule to predict what stable ions the atom is likely to form. Explain why the properties of ions differ from those of their parent atoms.

3 Section 1 Simple Ions Chemical Reactivity How much an element reacts depends on the electron configuration of its atoms. For example, oxygen will react with magnesium. In the electron configuration for oxygen, the 2p orbitals, which can hold six electrons, have only four: [O] = 1s 2 2s 2 2p 4 Neon has no reactivity. Its 2p orbitals are full: [Ne] = 1s 2 2s 2 2p 6

4 Section 1 Simple Ions Chemical Reactivity, continued Noble Gases Are the Least Reactive Elements Neon is a noble gas. The noble gases, which are found in Group 18 of the periodic table, show almost no chemical reactivity. The noble gases have filled outer energy levels. This electron configuration can be written as ns 2 np 6 where n represents the outer energy level.

5 Section 1 Simple Ions Chemical Reactivity, continued Noble Gases Are the Least Reactive Elements, continued The eight electrons in the outer energy level fill the s and p orbitals, making these noble gases stable. In most chemical reactions, atoms tend to match the s and p electron configurations of the noble gases. This tendency to have either empty outer energy levels or full outer energy levels of eight electrons is called the octet rule.

6 Section 1 Simple Ions Chemical Reactivity, continued Alkali Metals and Halogens Are the Most Reactive Elements An atom whose outer s and p orbitals do not match the electron configurations of a noble gas will react to lose or gain electrons so the outer orbitals will be full. When added to water, an atom of potassium (an alkali metal) gives up one electron in its outer energy level. Then, it has the s and p configuration of a noble gas. 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 1s 2 2s 2 2p 6 3s 2 3p 6

7 Section 1 Simple Ions Chemical Reactivity, continued Alkali Metals and Halogens Are the Most Reactive Elements, continued Chlorine, a halogen, is also very reactive. An atom of chlorine has seven electrons in its outer energy level. By gaining just one electron, it will have the s and p configuration of a noble gas. 1s 2 2s 2 2p 6 3s 2 3p 5 1s 2 2s 2 2p 6 3s 2 3p 6

8 Section 1 Simple Ions Valence Electrons Potassium after it loses one electron has the same electron configuration as chlorine after it gains one. Both are the same as that of the noble gas argon. [Ar] = 1s 2 2s 2 2p 6 3s 2 3p 6 The atoms of many elements become stable by achieving the electron configuration of a noble gas. The electrons in the outer energy level are known as valence electrons.

9 Section 1 Simple Ions Valence Electrons, continued Periodic Table Reveals an Atom s Number of Valence Electrons To find out how many valence electrons an atom has, check the periodic table. For example, the element magnesium, Mg, has the following electron configuration: [Mg] = [Ne]3s 2 This configuration shows that a magnesium atom has two valence electrons in the 3s orbital.

10 Section 1 Simple Ions Valence Electrons, continued Periodic Table Reveals an Atom s Number of Valence Electrons, continued The electron configuration of phosphorus, P, is [Ne]3s 2 3p 3. Each P atom has five valence electrons: two in the 3s orbital and three in the 3p orbital.

11 Section 1 Simple Ions Valence Electrons, continued Atoms Gain Or Lose Electrons to Form Stable Ions All atoms are uncharged because they have equal numbers of protons and electrons. For example, a potassium atom has 19 protons and 19 electrons. After giving up one electron, potassium still has 19 protons but only 18 electrons. Because the numbers are not the same, there is a net electrical charge.

12 Section 1 Simple Ions Valence Electrons, continued Atoms Gain Or Lose Electrons to Form Stable Ions, continued An ion is an atom, radical, or molecule that has gained or lost one or more electrons and has a negative or positive charge. The following equation shows how a potassium atom forms an ion with a 1+ charge. K K + + e - An ion with a positive charge is called a cation.

13 Section 1 Simple Ions Valence Electrons, continued Atoms Gain Or Lose Electrons to Form Stable Ions, continued In the case of chlorine, far less energy is required for an atom to gain one electron rather than give up its seven valence electrons to be more stable. The following equation shows how a chlorine atom forms an ion with a 1- charge. Cl + e - Cl - An ion with a negative charge is called an anion.

14 Section 1 Simple Ions Valence Electrons, continued Characteristics of Stable Ions Both an atom and its ion have the same number of protons and neutrons, so the nuclei are the same. The chemical properties of an atom depend on the number and configuration of its electrons. Therefore, an atom and its ion have different chemical properties.

15 Section 1 Simple Ions Valence Electrons, continued Many Stable Ions Have Noble-Gas Configurations Many atoms can form stable ions with a full octet. For example, Ca, forms a stable ion. The electron configuration of a calcium atom is: [Ca] = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 By giving up its two valence electrons in the 4s orbital, it forms a stable cation with a 2+ charge: [Ca 2+ ] = 1s 2 2s 2 2p 6 3s 2 3p 6 This electron configuration is like that of argon.

16 Section 1 Simple Ions Some Ions with Noble-Gas Configurations

17 Section 1 Simple Ions Valence Electrons, continued Some Stable Ions Do Not Have Noble-Gas Configurations Not all stable ions have an electron configuration like those of noble gases. Transition metals often form ions without complete octets. With the lone exception of rhenium, Re, the stable transition metal ions are all cations. Also, some elements, mostly transition metals, form stable ions with more than one charge.

18 Section 1 Simple Ions Stable Ions Formed by the Transition Elements and Some Other Metals

19 Section 1 Simple Ions Atoms and Ions Having identical electron configurations does not mean that a sodium cation is a neon atom. They still have different numbers of protons and neutrons. Ions and Their Parent Atoms Have Different Properties Both sodium and chlorine are very reactive. When they are mixed, a violent reaction takes place, producing a white solid table salt (sodium chloride). It is made from sodium cations and chloride anions.

20 Section 1 Simple Ions Atoms and Ions, continued Atoms of Metals and Nonmetal Elements Form Ions Differently Nearly all metals form cations. For example, magnesium metal, Mg, has the electron configuration: [Mg] = 1s 2 2s 2 2p 6 3s 2 To have a noble-gas configuration, the atom must either gain six electrons or lose two. Losing two electrons requires less energy than gaining six.

21 Section 1 Simple Ions Atoms and Ions, continued Atoms of Metals and Nonmetal Elements Form Ions Differently, continued The atoms of all nonmetal elements form anions. For example, oxygen, O, has the electron configuration: [O] = 1s 2 2s 2 2p 4 To have a noble-gas configuration, an oxygen atom must either gain two electrons or lose six. Acquiring two electrons requires less energy than losing six.

22 Section 2 Ionic Bonding and Salts Objectives Describe the process of forming an ionic bond. Explain how the properties of ionic compounds depend on the nature of ionic bonds. Describe the structure of salt crystals.

23 Section 2 Ionic Bonding and Salts Ionic Bonding Pyrite is a mineral that is shiny like gold, but it is made of iron cations and sulfur anions. Because opposite charges attract, cations and anions attract one another and an ionic bond is formed. The iron cations and sulfur anions of pyrite attract one another to form an ionic compound.

24 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Ionic Bonds Form Between Ions of Opposite Charge When sodium and chlorine react to form sodium chloride, sodium forms a stable Na + cation and chlorine forms a stable Cl - anion. The force of attraction between the 1+ charge on the sodium cation and the 1- charge on the chloride anion creates the ionic bond in sodium chloride. Sodium chloride is a salt, the scientific name given to many different ionic compounds.

25 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Ionic Bonds Form Between Ions of Opposite Charge, continued All salts are electrically neutral ionic compounds that are made up of cations and anions held together by ionic bonds in a simple, whole-number ratio. However, the attractions between the ions in a salt do not stop with a single cation and a single anion. One cation attracts several anions, and one anion attracts several cations. They are all pulled together into a tightly packed crystal structure.

26 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Transferring Electrons Involves Energy Changes Ionization energy is the energy that it takes to remove the outermost electron from an atom. The equation below shows this process for sodium. Na + energy Na + + e - With some elements, such as chlorine, energy is released when an electron is added. Cl + e - Cl - + energy

27 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Transferring Electrons Involves Energy Changes, continued The energy released when chlorine accepts and electron is less than the energy required to remove an electron from a sodium atom. Adding and removing electrons is only part of forming an ionic bond. The rest of the process of forming a salt supplies enough energy to make up the difference so that the overall process releases energy.

28 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Salt Formation Involves Endothermic Steps The process of forming the salt sodium chloride can be broken down into five steps. 1. Energy is needed to make solid sodium a gas. Na(solid) + energy Na(gas) 2. Energy is also required to remove an electron from a gaseous sodium atom. Na(gas) + energy Na + (gas) + e -

29 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Salt Formation Involves Endothermic Steps, continued 3. Chlorine exists as a molecule containing two chlorine atoms. Energy must be supplied to separate the chlorine atoms so that they can react with sodium. Cl Cl(gas) + energy Cl(gas) + Cl(gas) To this point, the first three steps have all been endothermic. These steps have produced sodium cations and chlorine atoms.

30 Section 2 Ionic Bonding and Salts Formation of Sodium Chloride

31 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Salt Formation Also Involves Exothermic Steps 4. An electron is added to a chlorine atom to form an anion. This step releases energy. Cl(gas) + e - Cl - (gas) + energy 5. When a cation and anion form an ionic bond, it is an exothermic process. Energy is released. Na + (gas) + Cl - (gas) NaCl(solid) + energy The last step is the driving force for salt formation.

32 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Salt Formation Also Involves Exothermic Steps, continued The energy released when ionic bonds are formed is called the lattice energy. This energy is released when the crystal structure of a salt is formed as the separated ions bond. Without this energy, there would not be enough energy to make the overall process spontaneous.

33 Section 2 Ionic Bonding and Salts Ionic Bonding, continued Salt Formation Also Involves Exothermic Steps, continued If energy is released when ionic bonds are formed, then energy must be supplied to break these bonds. As sodium chloride dissolves in water, water supplies energy for the Na + and Cl - ions to separate. Because of its much higher lattice energy, magnesium oxide does not dissolve well in water. There is not enough energy to separate the Mg 2+ and O 2- ions from one another.

34 Section 2 Ionic Bonding and Salts Ionic Compounds The ratio of cations to anions is always such that an ionic compound has no overall charge. Ionic Compounds Do Not Consist of Molecules Water is a molecular compound, so individual water molecules are each made of two hydrogen atoms and one oxygen atom. Sodium chloride is an ionic compound, so it is made up of many Na + and Cl - ions all bonded together to form a crystal. There are no NaCl molecules.

35 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Ionic Compounds Do Not Consist of Molecules, continued Metals and nonmetals tend to form ionic compounds and not molecular compounds. The formula CaO likely indicates an ionic compound because Ca is a metal and O is a nonmetal. In contrast, the formula ICl likely indicates a molecular compound because both I and Cl are nonmetals. Lab tests are used to confirm such indications.

36 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Ionic Bonds Are Strong Repulsive forces in a salt crystal include those between like-charged ions. Each Na + ion repels the other Na + ions. Each Cl - ion repels the other Cl - ions. Another repulsive force exists between the electrons of ions that are close together. Attractive forces include those between the positive nucleus of one ion and electrons of other ions.

37 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Ionic Bonds Are Strong, continued Attractive forces exist between oppositely charged ions and involve more than a single cation and anion. Six Na + ions surround each Cl - ion and vice versa. As a result, the attractive force between oppositely charged ions is significantly greater in a crystal than it would be if the ions existed only in pairs. Overall, the attractive forces are much stronger than the repulsive ones, so ionic bonds are strong.

38 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Ionic Compounds Have Distinctive Properties Most ionic compounds have high melting and boiling points because of the strong attraction between ions. To melt, ions cannot be in fixed locations. Because the bonds between ions are strong, a lot of energy is needed to free them. Still more energy is needed to move ions out of the liquid state and cause boiling, so ionic compounds are rarely gaseous at room temperature.

39 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Ionic Compounds Have Distinctive Properties, continued

40 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Liquid and Dissolved Salts Conduct Electric Current To conduct an electric current, a substance must satisfy two conditions: it must contain charged particles those particles must be free to move Ionic solids, such as salts, generally are not conductors because the ions cannot move. When a salt melts or dissolves, the ions can move about and are excellent electrical conductors.

41 Section 2 Ionic Bonding and Salts Sodium Chloride in Three Phases

42 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Salts Are Hard and Brittle Like NaCl, most ionic compounds are hard and brittle. Hard means that the crystal is able to resist a large force applied to it. Brittle means that when the applied force becomes too strong to resist, the crystal develops a widespread fracture rather than a small dent. Both properties are due to the patterns in which the cations and anions are arranged in all salt crystals.

43 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Salts Are Hard and Brittle, continued The ions in a crystal are arranged in a repeating pattern, forming layers. Each layer is positioned so that a cation is next to an anion in the next layer. The attractive forces between opposite charges resist motion. As a result, the ionic compound will be hard. Also, it will take a lot of energy to break all the bonds between layers of ions.

44 Section 2 Ionic Bonding and Salts Ionic Compounds, continued Salts Are Hard and Brittle, continued If a force causes one layer to move, ions of the same charge will be positioned next to each other. The cations in one layer are now lined up with other cations in a nearby layer. The anions are also. Because like charges are next to each other, they will repel each other and the layers will split apart. This is why all salts shatter along a line extending through the crystal known as a cleavage plane.

45 Section 2 Ionic Bonding and Salts Ionic Compounds, continued How to Identify a Compound as Ionic All ionic compounds are solid at room temperature. Tap the substance. Ionic compounds do not break apart easily and they fracture into tiny crystals. Heat the substance. Ionic compounds generally have high melting and boiling points. Use a conductivity device to find if the dissolved or melted substance conducts electricity. Dissolved and molten ionic compounds conduct electricity.

46 Section 2 Ionic Bonding and Salts Salt Crystals Despite their differences, the crystals of all salts are made of simple repeating units. These repeating units are arranged in a salt to form a crystal lattice, the regular pattern in which a crystal is arranged. These repeating patterns within a salt are the reason for the crystal shape that can be seen in most salts.

47 Section 2 Ionic Bonding and Salts Salt Crystals, continued Crystal Structure Depends on the Sizes and Ratios of Ions Formulas indicate ratios of ions. For example, the formula for NaCl indicates there is a 1:1 ratio of sodium cations and chlorine anions. Within a NaCl crystal, each Na + ion is surrounded by six Cl - ions, and each Cl - ion by six Na + ions. Because the edges of the crystal do not have this arrangement, they are locations of weak points.

48 Section 2 Ionic Bonding and Salts Salt Crystals, continued Crystal Structure Depends on the Sizes and Ratios of Ions, continued The arrangement of cations and anions to form a crystal lattice depends on the size of the ions and the ratio of cations to anions. For example, the salt calcium fluoride has one Ca 2+ ion for every two F - ions. The cations and anions in calcium fluoride also have a greater difference in size than those in NaCl.

49 Section 2 Ionic Bonding and Salts Salt Crystals, continued Crystal Structure Depends on the Sizes and Ratios of Ions, continued Because of the size differences of its ions and their ratio in the salt, the crystal lattice structure of calcium fluoride is different from that of sodium chloride. Each calcium ion is surrounded by eight fluoride ions. At the same time, each fluoride ion is surrounded by four calcium ions.

50 Section 2 Ionic Bonding and Salts Salt Crystals, continued Salts Have Ordered Packing Arrangements All salts are made of repeating units. The smallest repeating unit in a crystal lattice is called a unit cell. The ways in which a salt s unit cells are arranged are determined by X-ray diffraction crystallography. X-rays that strike ions in a crystal are deflected, while X-rays that pass through the crystal form a pattern. By analyzing this pattern, scientists can calculate the positions that the ions in the salt must have.

51 Section 3 Names and Formulas of Ionic Compounds Objectives Name cations, anions, and ionic compounds. Write chemical formulas for ionic compounds such that an overall neutral charge is maintained. Explain how polyatomic ions and their salts are named and how their formulas relate to their names.

52 Section 3 Names and Formulas of Ionic Compounds Naming Ionic Compounds Salts that are made of a simple cation and a simple anion are known as binary ionic compounds. The adjective binary indicates that the compound is made up of just two elements. Rules for Naming Simple Ions Simple cations borrow their names from the names of the elements. For example, K + is known as the potassium ion.

53 Section 3 Names and Formulas of Ionic Compounds Naming Ionic Compounds, continued Rules for Naming Simple Ions When an element forms two or more ions, the ion names include roman numerals to indicate charge. For example, the names of the two copper ions are: Cu + copper(i) ion Cu 2+ copper(ii) ion The name of a simple anion is also formed from the name of the element, but it ends in -ide. For example, Cl - is the chloride ion.

54 Section 3 Names and Formulas of Ionic Compounds Naming Ionic Compounds, continued The Names of Ions Are Used to Name an Ionic Compound The name of a binary ionic compound is made up of just two words: the name of the cation followed by the name of the anion. NaCl sodium chloride CuCl 2 copper(ii) chloride ZnS zinc sulfide Mg 3 N 2 magnesium nitride K 2 O potassium oxide Al 2 S 3 aluminum sulfide

55 Section 3 Names and Formulas of Ionic Compounds Writing Ionic Formulas Ionic compounds have a balance of positive and negative charges. Both ions in sodium chloride carry a single charge, so there are equal numbers of the ions Na + and Cl -. The formula for sodium chloride is written as NaCl to show this one-to-one ratio. The cation in zinc sulfide has a 2+ charge and the anion has a 2- charge. Thus, the formula ZnS shows a one-to-one ratio of ions.

56 Section 3 Names and Formulas of Ionic Compounds Writing Ionic Formulas, continued Compounds Must Have No Overall Charge In some ionic compounds, the charges of the cation and anion differ. For example, in magnesium nitride, the Mg 2+ ion, has two positive charges, and the N 3- ion, has three negative charges. The cations and anions must be combined in such a way that there are the same number of negative charges and positive charges.

57 Section 3 Names and Formulas of Ionic Compounds Writing Ionic Formulas, continued Compounds Must Have No Overall Charge, continued Three Mg 2+ cations are needed for every two N 3- anions for electroneutrality. That way, there are six positive charges and six negative charges. Subscripts are used to denote ion ratios. Therefore, the formula for magnesium nitride is Mg 3 N 2.

58 Section 3 Names and Formulas of Ionic Compounds Writing Ionic Formulas, continued Writing the Formula of an Ionic Compound Follow the following steps when writing the formula of a binary ionic compound: Write the symbol and charges for the cation and anion. The roman numeral shows which cation. Write the symbols for the ions side by side, beginning with the cation. To show it is a neutral compound, look for the lowest common multiple of the charges on the ions.

59 Section 3 Names and Formulas of Ionic Compounds Polyatomic Ions Instead of having ions made of a single atom, many ionic compounds have groups of atoms that are ions. Many Atoms Can Form One Ion A simple ion is monatomic, which means one-atom. A polyatomic ion is a charged group of two or more bonded atoms that can be considered a single ion. Unlike simple ions, most polyatomic ions are made of atoms of several elements. Like simple ions, polyatomic ions either positive or negative charge.

60 Section 3 Names and Formulas of Ionic Compounds Polyatomic Ions, continued Many Atoms Can Form One Ion, continued Consider the polyatomic ion ammonium, NH 4+. Ammonium is made of one nitrogen and four hydrogen atoms. They have a total of 11 protons but only 10 electrons. So the ammonium ion has a 1+ charge overall. This charge is not found on any one atom. Instead, it is spread across this group of bonded atoms.

61 Visual Concepts Comparing Monatomic, Diatomic, and Polyatomic Structures

62 Section 3 Names and Formulas of Ionic Compounds Polyatomic Ions, continued The Names of Polyatomic Ions Can Be Complicated The endings -ite and -ate in the name for a polyatomic indicate the presence of oxygen and the number of oxygen atoms present. For example, the formulas for two polyatomic ions 2-2- made from sulfur and oxygen are SO 3 and SO 4. The one with less oxygen takes the -ite ending, so 2- SO 3 is named sulfite. The ion with more oxygen takes the -ate ending, so 2- SO 4 is named sulfate.

63 Section 3 Names and Formulas of Ionic Compounds Polyatomic Ions, continued The Names of Polyatomic Ions Can Be Complicated, continued The presence of hydrogen is often indicated by an ion s name starting with hydrogen. The prefixes mono- and di- are also used. 2 HPO 4 HPO 4 is monohydrogen phosphate. is dihydrogen phosphate. The prefix thio- means replace an oxygen with a sulfur. K 2 S 2 O 3 is potassium thiosulfate.

64 Section 3 Names and Formulas of Ionic Compounds Polyatomic Ions, continued Naming Compounds with Polyatomic Ions Follow these steps when naming an ionic compound that contains one or more polyatomic ions: Name the cation. Recall that a cation is simply the name of the element. Name the anion. Recall that salts are electrically neutral. Name the salt. Recall that the name of a salt is just the names of the cation and anion.

65 Section 3 Names and Formulas of Ionic Compounds Formula of a Compound with a Polyatomic Ion Sample Problem A What is the formula for iron(iii) chromate?

66 Section 3 Names and Formulas of Ionic Compounds Formula of a Compound with a Polyatomic Ion, continued Sample Problem A Solution Determine the formula and charge for the iron(iii) cation. Fe 3+ Determine the formula and charge for the chromate polyatomic ion. 2- CrO 4

67 Section 3 Names and Formulas of Ionic Compounds Formula of a Compound with a Polyatomic Ion, continued Sample Problem A Solution, continued Because ionic compounds are electrically neutral, the total charges of the cations and anions must be equal. To balance the charges, find the least common multiple of the ions charges: for 2 and 3, it is 6. For 6 positive charges, you need 2 Fe 3+ ions. 2 3 = 6+

68 Section 3 Names and Formulas of Ionic Compounds Formula of a Compound with a Polyatomic Ion, continued Sample Problem A Solution, continued For 6 negative charges, you need 3 2- CrO 4 ions. 3 2 = 6- The formula must show 2 Fe 3+ ions and 3 2- CrO 4 ions. Parentheses are used whenever a polyatomic ion is present more than once. The formula for iron(iii) chromate is Fe 2 (CrO 4 ) 3.

69 Standardized Test Preparation Understanding Concepts 1. Which of the following can achieve the same electron configuration as a noble gas when the atom forms an ion? A. argon B. iron C. nickel D. potassium

70 Standardized Test Preparation Understanding Concepts 1. Which of the following can achieve the same electron configuration as a noble gas when the atom forms an ion? A. argon B. iron C. nickel D. potassium

71 Standardized Test Preparation Understanding Concepts 2. Why is an input of energy needed when forming NaCl? F. to change chlorine to a gas G. to add an electron to the chlorine atom H. to remove an electron from the sodium atom I. to bring together the sodium and the chloride ions

72 Standardized Test Preparation Understanding Concepts 2. Why is an input of energy needed when forming NaCl? F. to change chlorine to a gas G. to add an electron to the chlorine atom H. to remove an electron from the sodium atom I. to bring together the sodium and the chloride ions

73 Standardized Test Preparation Understanding Concepts 3. Which of the following is a characteristic of a salt? A. bends but does not shatter when struck sharply B. has the ability to conduct electric current in the solid state C. has the ability to conduct electric current in the liquid state D. melts at temperatures that are slightly higher than room temperature

74 Standardized Test Preparation Understanding Concepts 3. Which of the following is a characteristic of a salt? A. bends but does not shatter when struck sharply B. has the ability to conduct electric current in the solid state C. has the ability to conduct electric current in the liquid state D. melts at temperatures that are slightly higher than room temperature

75 Standardized Test Preparation Understanding Concepts 4. Which of the following pairs of elements are most likely to form an ionic bond? F. Br and Ca G. Br and N H. Ca and Mg I. Ca and Fe

76 Standardized Test Preparation Understanding Concepts 4. Which of the following pairs of elements are most likely to form an ionic bond? F. Br and Ca G. Br and N H. Ca and Mg I. Ca and Fe

77 Standardized Test Preparation Understanding Concepts 5. Explain why only a few metals are found in nature in their pure form, while most exist only as ores, which are metal-containing compounds.

78 Standardized Test Preparation Understanding Concepts 5. Explain why only a few metals are found in nature in their pure form, while most exist only as ores, which are metal-containing compounds. Answer: Metals lose their outer electrons easily to form ionic compounds with other elements.

79 Standardized Test Preparation Understanding Concepts 6. How can you tell from the number of valence electrons whether an element is more likely to form a cation or an anion?

80 Standardized Test Preparation Understanding Concepts 6. How can you tell from the number of valence electrons whether an element is more likely to form a cation or an anion? Answer: Elements that have only a few valence electrons form cations because it takes less energy to lose electrons. Elements with an outer energy level that is close to filled form anions.

81 Standardized Test Preparation Reading Skills Read the passage below. Then answer questions 7 and 8. In 1980, an oil drilling rig in Lake Peignur in Louisiana opened a hole from the lake to a salt mine 1,300 feet below ground. As the lake water flowed into the mine, it dissolved the salt pillars that were left behind to hold up the ceiling. When the entire mine collapsed, the resulting whirlpool swallowed a number of barges, a tugboat, trucks, and a large portion of an island in the middle of the lake. Eventually, the hole filled with water from a canal, leaving a much deeper lake.

82 Standardized Test Preparation Reading Skills 7. What was the most likely cause of the collapse of the salt mine? A. The salt melted due to the temperature of the water. B. Water dissolved the ionic sodium chloride, leaving no supports. C. Water is denser than salt, so the salt began to float, moving the columns. D. The open hole exposed the salt pillars to the air and they had a chemical reaction with oxygen.

83 Standardized Test Preparation Reading Skills 7. What was the most likely cause of the collapse of the salt mine? A. The salt melted due to the temperature of the water. B. Water dissolved the ionic sodium chloride, leaving no supports. C. Water is denser than salt, so the salt began to float, moving the columns. D. The open hole exposed the salt pillars to the air and they had a chemical reaction with oxygen.

84 Standardized Test Preparation Reading Skills 8. When there is no water present, the pillars in a salt mine are capable of holding the weight of the ceiling because F. salt is held together by strong ionic bonds. G. salt melts as it is mined and then reforms to a hard crystal. H. salt contains sodium, which gives it the properties of metal. I. salt does not crumble due to the low temperatures found below ground level.

85 Standardized Test Preparation Reading Skills 8. When there is no water present, the pillars in a salt mine are capable of holding the weight of the ceiling because F. salt is held together by strong ionic bonds. G. salt melts as it is mined and then reforms to a hard crystal. H. salt contains sodium, which gives it the properties of metal. I. salt does not crumble due to the low temperatures found below ground level.

86 Standardized Test Preparation Interpreting Graphics Many transition metals are capable of forming more than one type of stable ion. The properties of compounds formed by one ion are often different from those formed by an ion of the same element have a different charge. Use the table below to answer questions 9 12.

87 Standardized Test Preparation Interpreting Graphics 9. How do the cations formed by transition metals differ from those formed by metals in the first two columns of the periodic table? A. Transition metals lose more electrons. B. All of the transition metal ions have a positive charge. C. Transition metals generally do not ionize to a noble gas configuration. D. All of the transition metals are capable of forming several different ions.

88 Standardized Test Preparation Interpreting Graphics 9. How do the cations formed by transition metals differ from those formed by metals in the first two columns of the periodic table? A. Transition metals lose more electrons. B. All of the transition metal ions have a positive charge. C. Transition metals generally do not ionize to a noble gas configuration. D. All of the transition metals are capable of forming several different ions.

89 Standardized Test Preparation Interpreting Graphics 10. Which of these metals forms ions with a noble gas electron configuration? F. copper G. germanium H. hafnium I. platinum

90 Standardized Test Preparation Interpreting Graphics 10. Which of these metals forms ions with a noble gas electron configuration? F. copper G. germanium H. hafnium I. platinum

91 Standardized Test Preparation Interpreting Graphics 11. Based on the stable ions in the illustration, which of these compounds is most likely to exist? A. Fe 2 O B. FeO 2 C. Hg 2 O D. Mo 3 O 2

92 Standardized Test Preparation Interpreting Graphics 11. Based on the stable ions in the illustration, which of these compounds is most likely to exist? A. Fe 2 O B. FeO 2 C. Hg 2 O D. Mo 3 O 2

93 Standardized Test Preparation Interpreting Graphics 12. How many different ionic compounds exist that consist of only iron and chlorine?

94 Standardized Test Preparation Interpreting Graphics 12. How many different ionic compounds exist that consist of only iron and chlorine? Answer: 2