Ionic Compounds and Ionic Bonding

Transcription

1 Ionic Compounds and Ionic Bonding Table of Contents: Ionic Compounds and Ionic Bonding Periodic Table Review Valence Electrons and the Octet Rule Ions Ionic Bonding Properties of Ionic Compounds Predicting an Ionic Compound's Formula Naming Ionic Compounds Click on the topic to go to that section Formulas and Names of Ionic Compounds with Transition Metals Polyatomic ions Formula and Names of Compounds with Polyatomic ions (Ternary Ionic Compounds) Polyatomic Patterns

2 Periodic Table Review Return to Table of Contents Periodic Table Review The periodic table is "periodic" because of certain trends that are seen in the elements. Some of these trends are atomic size, ionization energy, electronegativity and metallic character. Elements from the same family/group have similar chemical properties because of their similar electron configuration.

3 The Periodic Table of the Elements The periodic table can be divided into three large classifications of elements. What type of elements are highlighted in blue, in yellow and in pink? What is unique about the elements that are highlighted in pink? B Si Ge As Sb Te? Metallic Character of the Elements When comparing elements in a period (row), elements on the left generally have a "weaker" pull on their electrons due to the fewer protons in the nucleus. The weaker the pull on electrons, the more easily the electrons are lost, and the greater the metallic character of the element. More metallic Less metallic Non metallic Most metallic B Si Ge As Sb Te?

4 Metallic Character of the Elements As one moves down a column in the periodic table, atoms become larger due to more filled orbitals. The larger the atom, the farther the outer electrons are from the nucleus, and the easier it is for the atom to lose those electrons. The easier it is to lose electrons, the more metallic the element. More metallic Less metallic Non metallic Most metallic B Si Ge As Sb Te? 1 Elements exhibit similar physical and chemical properties. A B C D E with similar chemical symbols with similar atomic masses in the same period of the periodic table on opposite sides of the periodic table in the same group of the periodic table

5 2 Which pair of elements would you expect to exhibit the greatest similarity in their physical and chemical properties? A B C D E Li, Na Cs, Ba Ca, Si Ga, Ge C, O 3 Which of the following is a nonmetal? A W B Sr C Os D Ir E S

6 4 Potassium is a and chlorine is a. A B C D E metal, nonmetal metal, metal metal, metalloid metalloid, nonmetal nonmetal, metal #. Which element from each pair is more metallic? Sodium or Sulfur? Calcium or Francium? Magnesium or Fluorine?

7 Valence Electrons and the Octet Rule Return to Table of Contents Octet Rule Octet Rule: Atoms will gain, lose, or share electrons in order to have complete outer shells of electrons (This gives the atom stability). A full outer shell in most atoms will contain 8 electrons: 2 electrons in the s subshell and 6 electrons in the p subshell ( s 2 p 6 configuration) Small atoms, like Li, Be, and B, will lose electrons to have a full s 2 configuration. This is called a duet. Which elements on the periodic table have a complete outer shell? What is true about these elements relative chemical reactivity?

8 Valence Electrons Valence electrons are the electrons in the highest occupied energy level of an element s atoms. Valence electron The valence electrons determine the chemical properties of an element. Why do you think this would be true? To find the number of valence electrons in an atom of a representative element (elements found in the s and p blocks), simply look at its group number. Atoms in group 3 have 3 valence electrons, atoms in group 17 have 7 valence electrons, etc. Valence Electrons Number of valence 1 2 electrons in neutral atoms: There is one exception: helium has only 2 valence electrons.

9 Valence Electrons Lithium 1s 2 2s 1 has 1 valence electron in its outermost, n=2, energy level. Oxygen 1s 2 2s 2 2p 4 has 6 valence electrons 5 How many valence electrons does potassium have? A 3 B 1 C 19 D 4 E 8

10 6 How many valence electrons does Aluminum have? A 5 B 7 C 3 D 27 E 13 7 How many valence electrons does Barium have? A 1 B 2 C 52 D 3 E 6

11 8 Arsenic (As) has 6 valence electrons. True False Ions Return to Table of Contents

12 Ions Ions are atoms or groups of atoms that have become charged by either gaining or losing electrons. Cations are positive and are formed by elements on the left side of the periodic chart (metals). Anions are negative and are formed by elements on the right side of the periodic chart (nonmetals). The Formation of Cations Metals usually give up/lose valence electrons to become more stable. This results in a noble gas electron configuration (usually 8 electrons, but 2 in the case of He) in their now outermost shell. Na : 1s 2 2s 2 2p 6 3s 1 Na +1 : 1s 2 2s 2 2p 6 3s 2p Ne atom 2s 1s Loss of valence electrons How many electrons does the Na + ion have?

13 The Formation of Cations Na atom Na+ ion loses e 11p 11e 11p 10e The Na + ion is smaller than the Na atom. Do you remember what factors cause this reduction in size? The Formation of Cations Cations of Group 1A elements always lose 1 electron and have a charge of 1+. Cations of Group 2A elements always lose 2 electrons and have a charge of 2+. Mg Mg e Mg atom (electrically neutral, charge = 0) Mg ion (+2 indicates 2 units of positive charge) (2 in front of e indicates 2 units of negative charge)

14 The Formation of Anions Nonmetals usually gain valence electrons. This results in a noble gas configuration of 8 electrons in their outer shell Cl 1s 2 2s 2 2p 6 3s 2 3p 5 Cl 1s 2 2s 2 2p 6 3s 2 3p 6 Ar atom 3p 3s 2p 2s How many electrons does the Cl have? The Formation of Anions Cl atom Cl ion 17P 17e Gains an e 17p 18e Single anions are named with a shortened element name and an "ide" ending. Cl is named chloride.

15 The Formation of Anions Anions of Group 15 elements always gain 3 electrons and have a charge of 3 Anions of Group 16 elements always gain 2 electrons and have a charge of 2 Anions of Group 17 elements always gain 1 electron and have a charge of 1 Consider Group 14 elements, what common charge(s) would you predict for these elements? Formation of Ions and Metallic Character The more metallic an element, the easier it loses electrons, resulting in the formation of cations. The less metallic an element, the greater the hold on electrons, and the less likely they are to form cations.

16 Ion Symbols To write the symbol for an ion, write the symbol of the element and show the ion charge as a superscript, with the number value first followed by the + or sign. Ex: Ca 2+ When an ion has a charge of 1+ or 1, it is not necessary to put the 1 in the ion symbol, just the + or sign. Ex: F 1 may simply be written F. 9 Metals tend to electrons and nonmetals tend to electrons. A B C D E gain, gain lose, lose gain, lose lose, gain neither, they keep their electrons

17 10 Anions tend to be and cations tend to be. A B C D E metals, metals nonmetals, nonmetals metals, nonmetals nonmetals, metals metalloids, metalloids 11 Metals lose electrons to form cations True False

18 12 Anions are formed from nonmetals True False 13 Nonmetals tend to lose electrons forming ions True False

19 14 This is the ion formed from a calcium atom A Ca + B Ca 2+ C Ca D Ca 2 15 Phosphorous forms an ion with a charge of. A 1+ B 2 C 3+ D 3 E 2+

20 16 Aluminum forms an ion with a charge of. A 2+ B 1 C 3+ D 2 E 0 17 Of the following, contains the greatest number of electrons. A P 3+ B P C P 2 D P 3 E P 2+

21 18 Oxygen forms an ion with a charge of. A 2 B 2+ C 3 D 3+ E Iodine forms an ion with a charge of. A 7 B 1+ C 2 D 2+ E 1

22 20 This is the ion formed from nitrogen A N B N 2 C N 3+ D N 3 21 Predict the charge of the most stable ion of S? A 3+ B 1 C 6+ D 2+ E 2

23 22 What would be the expected charge on the gallium (Ga) ion? A +1 B +2 C +3 D +13 E 5

24 Ionic Bonding Return to Table of Contents

25 Introduction to Chemical Bonds There are three basic types of bonds: Ionic The electrostatic ( positive to negative) attraction between ions Covalent The sharing of electrons between atoms Metallic Each metal atom bonds to other metals atoms within a "sea" of electrons (covered in a later unit)

26 Electronegativity Electronegativity is how strongly an atom attracts electrons from a neighboring atom. Electronegativity Electronegativity increases left to right across the periodic table, and decreases as you move down a column. Flourine is the most electronegative element. Francium is the least electronegative element.

27 Ionic Bonding Atoms with a high electronegativity will be able to attract electrons away from atoms with a much lower electronegativity. This removal of electrons can occur when the difference in electronegativity between the two atoms is approximately 1.7 or higher. Once a positive and negative ion are formed, they will be attracted to each other via the electrostatic force. Ionic Bonding Neutral atom 1 valence electron Low Electronegativity Neutral atom 7 valence electrons High Electronegativity + Cation Anion

28 Ionic Bonding The atom with high electronegativy attracts valence electrons from the atom with lower electronegativity. Generally when a metal reacts with a non metal, the metal loses electrons to form a cation and the non metal gains electrons to form an anion. When the atoms become oppositely charged ions the electrostatic force of attraction brings them together. Electrostatic force of attraction = bond + Cation Anion Ionic Bonding Compounds composed of cations and anions are called ionic compounds. Although they are composed of ions, ionic compounds are electrically neutral since the electrons being lost by the metal are the same electrons being gained by the non metal. The electrostatic forces that hold ions together in ionic compounds are called ionic bonds.

29 Ionic Bonds The electron transfer process in creating an ionic bond: Na Cl The dots represents the valence electrons in an atom. click here for an animation of this reaction Ionic Bonding An electronegativity difference of approximately 1.7 can only occur between a metal and a nonmetal.

30 23 Which pair of atoms will form an ionic bond? A B C D Li and Ne K and Br K and Cs S and Cl 24 Which pair of atoms will form an ionic bond? A B C D Li and Be Na and Mg K and Ca Na and Cl

31 25 An ionic bond would form between Sc and F? True False 26 Which of the following compounds would you expect to be ionic? A H2 O B CO 2 C SrCl 2 D SO 2 E H 2 S

32 Properties of Ionic Compounds Return to Table of Contents Properties of Ionic Compounds 1. They are crystalline solids at room temperature The cations and anions are arranged in a repeating geometric pattern.

33 Properties of Ionic Compounds 2. They have high melting points due to the strength of the ionic bonds. 3. They conduct electricity when melted (molten) or dissolved in water (aqueous) due to the ability of the ions to move around. Formula Units A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. A formula unit is the lowest whole number ratio of ions in an ionic compound. This is also called the empirical formula.

34 Chemical formulas Chemical formulas are written using the chemical symbol followed by a subscript indicating the number of that atom or ion. NaCl indicates a ratio of 1 Na + : 1 Cl H 2 O indicates a ratio of 2 H : 1 O Predicting an Ionic Compound's Formula Return to Table of Contents

35 Predicting an Ionic Compound Formula Potassium (K) with an electronegativity of 0.8 and oxygen (O) with an electronegativity of 3.5 will form an ionic compound. What is the formula for an ionic compound of potassium and oxygen? How many additional valence electrons does oxygen need? 2 How many valence electrons does potassium have? 1 How many potassium atoms will it take to give oxygen the electrons it needs? 2 The metal is always first in the formula, followed by the nonmetal. K K O The formula unit is K 2 O Predicting an Ionic Compound Formula What is the formula for an ionic compound of Mg and N? How many additional valence electrons does N need? 3 How many valence electrons does Mg have to offer? 2 How many Mg atoms will it take to give how many N the electrons it needs? (Find the lowest common multiplier first.) Mg Mg Mg N N 3 Mg : 2 N The formula unit is Mg 3 N 2

36 Ionic compounds are neutral Mg Mg Mg N N As you can see in the diagram, all electrons lost by a Mg must be taken by a N. This causes the total positive charge (electrons lost) to be equal to the total negative charge (electrons gained). Predicting an Ionic Compound Formula Example: Write the formula for calcium sulfide. Step 1: Identify the cation & write its common ion Calcium is in group 2: Ca 2+ Step 2: Identify the anion & write its formula Sulfur is in group 6: S 2 Step 3: Only one cation and one anion are needed to make a neutral compound. Step 4: The formula is written CaS

37 27 The formula for barium sulfide is Ba2 S 2. True False 28 The formula for the ionic compound between Mg and S is: A Mg 2 S 2 B MgS C MgS 2 D SMg E I don't know how to do this.

38 29 The formula for the ionic compound between Cs and O is: A CsO 2 B OCs 2 C Cs 2 O D OCs 2 E I don't know how to do this. 30 The ionic compound formed between Ca and N is: A CaN B Ca 2 N 2 C Ca 3 N 2 D Ca 2 N 3 E I don't know how to do this.

39 31 The ionic compound formed between Al and O A Al 3 O 2 B Al 2 O 3 C AlO D Al 2 O 2 E I don't know how to do this. 32 What is the ionic compound formed between Ca and Al? A CaAl B Ca 3 Al 2 C Al 2 Ca 3 D No compound is formed.

40 33 What is the ionic compound formed between P and Br? A P 3 Br B BrP C This compound is not considered ionic D (BrP) 2 E I don't know how to do this. 34 What is the formula for sodium phosphide? A SP 3 B NaP C Na 3 P D NaP 3 E I don't know how to do this.

41 35 What is the formula for strontium bromide? A SrBr B SrBr 2 C Sr 2 Br D BrSr 2

42 Naming Ionic Compounds Return to Table of Contents Naming Binary Ionic Compounds Cations Many cations have the same name as the original, neutral atom. Charge Formula Name H + Li + K + Cs + Ag + Mg 2+ Ca 2+ Ba 2+ Cd 2+ Al 3+ Hydrogen ion Lithium ion Potassium ion Cesium ion Silver ion Magnesium ion Calcium ion Barium ion Cadmium ion Aluminum ion

43 Naming Binary Ionic Compounds Anions All monoatomic anions end in " ide". Group 15 Group 16 Group 17 Nitride N 3 2 Oxide O Fluoride F Phosphide P 3 Sulfide S 2 Chloride Cl Bromide Br Iodide I Naming Binary Ionic Compounds Binary (two element) compounds are named by writing the name of the cation followed by the name of the anion. The name of the cation is the same as the metal name. The name of the anion is the name of the non metal with the suffix changed to ide. Examples: NaCl = sodium chloride KI = potassium iodide Li 2 S = lithium sulfide

44 36 The correct name for Na2 S is A B C D Sodium sulfate Sodium sulfide Di sodium sulfide Sulfur nitride 37 The correct name for SrO is. A B C D E strontium oxide strontium hydroxide strontium peroxide strontium monoxide strontium dioxide

45 38 The correct name for Al2 O 3 is. A B C D E aluminum trioxide dialuminum oxide dialuminum trioxide aluminum oxide aluminum hydroxide

46 Names and Formulas of Ionic Compounds with Transition Metals Return to Table of Contents

47 Cations formed by Transition Elements Recall that s block metals and some p block elements like aluminum have only one possible ionic charge, based on the Octet Rule. However, most transition metals (d block elements) can form more than one type of cation with different charge. Sn, Pb from the p block are called posttransition metals and will form more than one type of ion and behave like transition metals. Cations formed by Transition Elements The 2+ charge is very common among the transition metals since they lose their two "s" electrons first, before losing others from their "d" orbital. book/contents/m51186.html

48 Cations Formed by Transition Elements Only common transition metals are shown. Silver, cadmium and zinc only form one cation, Ag +, Cd 2+ and Zn 2+ Note the two mercury cations, one is a single atom, the other is made up of two atoms together this is called a polyatomic ion. Silver, Zinc, and Cadmium Ions Why do these ions only have one possible charge? Let's look at their electron configurations. The "d" orbital of both zinc and cadmium are full and therefore very stable so the only electrons it will lose are the two "s" electrons... Zn: [Ar]4s 2 3d 10 Zn 2+ : [Ar]3d 10 The "d" orbital is also full with silver as it has largely taken an electron from it's own "s" orbital to make stabilize the "d" orbital. Therefore, it only has 1 electron left to lose. Ag: [Kr]5s 1 4d 10 Ag + : [Kr]4d 10

49 Cations formed by Transition Elements We will use the Stock naming system. The name of the transition metal MUST be followed by Roman Numerals indicating its charge. Formula Cu +1 Co +2 Fe +2 Mn +2 Pb +2 Name Copper (I) ion Cobalt (II) ion Iron (II) ion Manganese (II) ion lead (II) ion Cr +3 Chromium (III) ion Fe +3 Iron (III) ion What would be the names of Cu 2+ and Mn 7+? Writing Formulas with Transition Metals The charge on the cation is indicated by the Roman numeral, as shown in this example. Iron (III) oxide Fe 3+ O 2 Fe 2 O 3 Write ion formulas. Determine ratio of cations to anions. Reduce if necessary.

50 Writing Formulas with Transition Metals The charge on the cation is indicated by the Roman numeral, as shown in this example. Tin (IV) oxide Sn 4+ O 2 Write ion formulas. Sn 2 O 4 Determine ratio of cations to anions. SnO 2 Reduce if necessary. 39 Which metal is capable of forming more than one cation? A B C D E K Cs Ba Al Sn

51 40 Which metal is not capable of forming more than one cation? A B C D E Cu Au Fe Sn Al Naming a Compound with a Transition Metal In order to correctly name a formula containing a transition metal, it is necessary to first determine the charge on the cation. Since all compounds are neutral, the total positive cation charge must equal the total negative anion charge AND since anion charges don't vary, we can use this formula to find the charge on the transition metal. Total cation charge + Total anion charge = 0 (charge of cation) (# of cations) + (charge of anion) (# of anions) = 0

52 Example Formula with Transition Metals In the case of FeCl 3, we know there is 1 Fe and 3 Cl, and the charge on Chloride is always 1. Fill in these values and solve for the charge on Fe. (charge of cation) (# of cations) +(charge of anion) (# of anions) = 0 (x) (1) + ( 1) (3) = 0 So x = 3 and the cation is Fe 3+. The compound is Iron (III) Cloride Formulas with Transition Metals Here's another practice problem. CrO: Cr 1 O 1 Determine the charge of O. Cr 2+ O 2 Since O has charge of 2, Cr must have a charge of 2+ Cr 2 O 2 Chromium (II) Oxide

53 41 The correct name of the compound V 2 O 3 is vanadium(ii)oxide. True False 42 The correct name for Cu 3 N is: A copper nitride B copper (I) nitride C copper (II) nitride D copper(iii)nitride E copper(iii) nitrogen

54 43 The name of FeCl3 is A B C D iron chloride iron (II) chloride iron (III) chloride iron(i)chloride 44 The correct formula for tin (IV) oxide is: A SnO 2 B SnO C Sn 4 O 4 D Sn 4 O 2

55 45 The formula for copper (II) sulfide is A CuS 2 B CuS C Cu 2 S 2 D (CuS) 2 E Cu 2 S 46 Which one of the following compounds is copper(i) chloride? A CuCl B CuCl 2 C Cu 2 Cl D Cu 2 Cl 2 E Cu 3 Cl 2

56 47 The charge on the cation in the salt Fe2 O 3 is. A 1+ B 2+ C 3+ D 5 E 6 [*] 48 What is the charge on zirconium ion in ZrO2? A 2+ B 4+ C 1+ D 2 E 3+

57 Polyatomic Ions Return to Table of Contents Polyatomic Ions A polyatomic ion is a group of atoms bonded together that have a charge and acts like a single unit or ion. They are commonly part of an ionic compound, as either the cation or the anion. Sulfate = (SO 4 ) 2 Nitrate = (NO 3 ) Carbonate = (CO 3 ) 2 When writing formulas for compounds containing polyatomic ions, use ( ) to keep the atoms together. Do not change the subscripts inside the "( )"

58 Polyatomic Ions Most of the polyatomic ions contain oxygen atoms. Many anions names end with ite or ate In ite/ate pairs, the ion with fewer oxygen atoms will have the ite ending Examples: sulfite /sulfate nitrite /nitrate Note that the suffix does not indicate the actual number of O atoms.

59 . Polyatomic Ions Familiarize yourself with the polyatomic ions on your reference sheet Be careful of ide, ite, and ate! H + = proton or hydrogen ion ] or bicarbonate Formulas and Names of Ionic Compounds with Polyatomic Ions (Ternary Ionic Compounds) Return to Table of Contents

60 Writing Formulas for Ternary Ionic Compounds Ternary ionic compounds, compounds that contain 3 or more elements, are neutral, just like binary ionic compounds. Therefore, the goal is to find the lowest ratio of cations to anions that will yield a neutral compound. This ratio is represented in a formula unit. Examples of formula units CaCO 3 Zn(C 2 H 3 O 2 ) 2 AgNO 3 Na 2 SO 3 To write a formula Writing Formulas for Ternary Ionic Compounds Example: Write the formula for lithium phosphate. Step 1: Identify the cation & write its formula Lithium is in group 1 > Li + Step 2: Identify the anion & write its formula Phosphate is a polyatomic ion > PO 4 3 Step 3: Find the ratio of cation to polyatomic anion Li 3 (PO 4 ) 1 or simply Li 3 (PO 4 )

61 Writing Formulas for Ternary Ionic Compounds Example 1: Write the formula for lithium chlorate. Example 2: Write the formula for manganese(iii) carbonate. Li +1 (ClO 3 ) 1 = Li(ClO 3) = LiClO 3 Move for Note: The ( ) are removed because only 1 chlorate ion is present. Mn 3+ (CO 3 ) 2 = Mn 2(CO 3 ) 3 Move for Note: The ( ) are needed here because more than one carbonate ion are present 49 The formula for aluminum phosphate is: A AlPO 4 B Al 3 (PO 4 ) C Al 2 (PO 4 ) 3 D Al 3 (PO 4 ) 3

62 50 What would be the correct formula for cobalt(iii) carbonate? A Co 3 CO 3 B Co 2 CO 3 C Co 2 (CO 3 ) 3 D Co 3 (CO 3 ) 2 E CoCO 3 51 The formula for sodium hydroxide is A B Na (OH)2 NaOH C Na(OH 2 ) D Na(HO) E NaOH 2

63 52 The formula for calcium sulfate is A CaSO 4 B Ca 2 (SO 4 ) 2 C Ca(SO 3 ) D Ca 2 (SO 3 ) 2 E CaS 53 How many nitrate ions are present in the formula of aluminum nitrate? (Write the formula first to find out.) A 1 B 2 C 3 D 4 E 5

64 54 How many total ions (cations and anions) are present in the formula of lithium acetate? A 1 B 2 C 3 D 4 E 5 Writing Formulas for Ionic Compounds Complete the table by filling in the formula for the ionic compound formed by each pair of cations and anions, as shown for the first pair.

65 Writing Formulas for Ternary Ionic Compounds Write the formula for the following compounds: 1. Magnesium iodide MgI 2 2. Calcium sulfite CaSO 3 3. Barium hydrogen carbonate Ba(HCO 3 ) 2 Move for answer 4. Iron (III) phosphate FePO 4 Naming Ternary Ionic Compounds Ternary ionic compounds contain three or more different elements due to the presence of polyatomic ion(s). Just as in binary ionic compounds, the name of the cation is given first, followed by the name of the anion. Names of ternary compounds often end in ite or ate. Examples CaCO 3 Zn(C 2 H 3 O 2 ) 2 AgNO 3 Na 2 SO 3 calcium carbonate zinc acetate silver nitrate sodium sulfite Move f answe

66 55 The correct name for NaClO is A B C sodium chlorate sodium chloride sodium chlorite D sodium chloride oxide E sodium hypochlorite 56 Mg(HCO3 ) 2 is A B C D Magnesium carbonate Magnesium hydrogen carbonate Magnesium hydroxide Magnesium carboxide E Magnesium dibicarbonate

67 57 Ammonium carbonate is A NH 4 CO 3 B (NH 4 ) 2 CO 3 C NH 4 (CO 3 ) 2 D (NH 4 ) 2 CO 2 Naming Ternary Ionic Compounds If the formula involves a transition or post transition element, you must first deduce the charge so it can be included in the name. For example: Name Cu 2 CO 3 1. Determine the charge of the polyatmoic anion CO 3, which is 2 Cu 2 (CO 3 ) 2 2. Determine the charge of the cation, Cu carries a +1 charge This compound is called copper(i) carbonate

68 58 What is the name for Ga 2 (SO 3 ) 3? A gallium sulfite B gallium (I) sulfite C gallium (III) sulfite D gallium (III) sulfate 59 Which is the name for AuF 3? A gold (I) flouride B gold(iii) flouride C gold flouride D gold flourine E gold triflouride

69 60 What is the name for Sn(CO 3 ) 2? A tin carbonate B tin(ii) carbonate C tin carbide D tin tetracarbonate E tin (IV) carbonate