Ionic_Bonding_&_Ionic_Compounds_Presentation_v_1.1.notebook. October 26, Chemical Bonds. Notebook 4 Ionic Compounds and Ionic Bonding

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1 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook hemical onds Notebook 4 Ionic ompounds and Ionic onding There are three basic types of bonds: Ionic The electrostatic attraction between ions ovalent The sharing of electrons between atoms Metallic Each metal atom bonds to other metals atoms within a mobile "sea" of electrons (not covered until P hemistry) Ionic onding Electronegativity is how strongly an atom attracts electrons. toms with a high electronegativity will be able to attract electrons away from atoms with a much lower electronegativity. Ionic onding n electronegativity difference of 1.7 can only occur between a metal and a nonmetal. This removal of electrons can occur when the difference in electronegativity between the two atoms is more than 1.7 Once a positive and negative ion are formed, they will be attracted to each other via the electrostatic force: F = k q 1 q 2 r 2 1 Which pair of atoms will form an ionic bond? 2 Which pair of atoms will form an ionic bond? Li and Ne Li and e K and r Na and Mg K and s K and a S and l Na and l 1

2 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook The Octet Rule In forming compounds, atoms tend towards the electron configuration of a noble gas. toms in the first three groups (1 3) will lose electrons and become cations (think: metals). Ions formed by Representative Elements The charges of the ions of representative elements (s block and p block elements) can be determined by the position on the periodic table. Recall that elements shown here gain or lose electrons to establish a noble gas electron configuration. toms in groups 5 7 (or 15 17) will gain electrons and become anions (think: nonmetals). toms in group 8 (or 18) are the noble gases, which do not generally gain or lose electrons. Valence Electrons Valence electrons are the electrons in the highest occupied energy level of an element s atoms. The number of valence electrons largely determines the chemical properties of an element. To find the number of valence electrons in an atom of a representative element, simply look at its group number. 3 How many valence electrons does luminum have? toms in group 3 have 3 valence electrons, atoms in group 7 have 7 valence electrons, etc. 4 How many valence electrons does arium have? 1 2 The Formation of ations Metals usually give up valence electrons This results in a noble gas (8 electron) outer shell. Na : 1s 2 2s 2 2p 6 3s 1 Na +1 : 1s 2 2s 2 2p 6 Ne atom 52 3 Loss of valence electrons The configuration of the Sodium ion is the same as Neon 2

3 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook The Formation of ations The Formation of ations ations of Group 1 elements always have a charge of 1+. loses e ations of Group 2 elements always have a charge of 2+. Na atom 11p 11e Na+ atom 11p 10e The Formation of nions The gain of negatively charged electrons by a neutral atom produces an anion. n anion is an atom or a group of atoms with a negative charge. The Formation of nions gain of one electron gives chlorine an octet and converts a chlorine atom into a chloride ion. l: 1s2 2s2 2p6 3s2 3p5 l 1s2, 2s2, 2p6, 3s2, 3p6 r atom The name of a monoatomic anion typically ends in ide. Nonmetals from Group 5 and above gain electrons to form anion. Group 4 elements do not form cations or anions chloride ion has the same electron configuration as argon. The Formation of nions The Formation of nions nions of Group 5 elements have a charge of 3 l atom 17P 17e Gains an e l ion 17p 18e nions of Group 6 elements always have a charge of 2 nions of Group 7 elements have a charge of 1 3

4 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook 5 The ion formed from a calcium atom 6 Nonmetals tend to lose electrons forming ions a + a 2+ True False a a 2 7 Metals lose electrons to form cations 8 The ion formed from nitrogen True False N N 2 N 3+ N 3 9 nions are formed from nonmetals Formation of Ionic ompounds True False ompounds composed of cations and anions are called ionic compounds. lthough they are composed of ions, ionic compounds are electrically neutral. 4

5 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook Ionic onds The electrostatic forces that hold ions together in ionic compounds are called ionic bonds. Ionic bonds are formed by the "harpoon method". Ionic onds For instance, when sodium and chlorine are close together, sodium's valance electron flies off and "harpoons" the chlorine atom. The result is a sodium cation (+) next to a chloride anion ( ) These oppositely charged two ions attract: they reel one another together to form an ionic bond. Na l Na+ l 1s 2 2s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 3p 5 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 6 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 6 Ne r Na l Ionic onds Formula Units ary/flash_viewer.php?oid=1349 &mid=55 try/chemistry ii/chemical bonding/ionicbonding animation.php chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. formula unit is the lowest whole number ratio of ions in an ionic compound. Every ionic compound has a 3 array of positive and negative ions. Properties of Ionic ompounds They are crystalline solids at room temperature They have high melting points They conduct electricity when melted (molten) or dissolved in water (aqueous) Predicting an Ionic ompound Formula Potassium (K) with an electronegativity of 0.8 and oxygen (O) with an electrogegativity 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 want? 2 How many valence electrons does potassium have? 1 How many potassium atoms will it take to give oxygen the electrons it needs? 2 K K O The formula unit is K 2O 5

6 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook Predicting an Ionic ompound Formula Mg Mg Mg What is the formula for an ionic compound of Mg and N? How many additional valence electrons does N want? 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.) N N 3 Mg : 2 N The formula unit is Mg 3N 2 Predicting an Ionic ompound Formula If you don't like finding least common multipliers, you can use this alternative method: 1. Write down the ions side by side along with their charge. lways write the metal first. 2. "riss cross" the numerical values of the charges. 3. Reduce subscripts to lowest ratio. Mg Mg Mg N N Predicting an Ionic ompound Formula Example: Write the formula for calcium sulfide. Step 1: Identify the cation & write its common ion alcium is in group 2 a 2+ Step 2: Identify the anion & write its formula Sulfur is in group 6 S 2 Predicting an Ionic ompound Formula What is the compound formed between Mg and S? Mg +2 S 2 Mg 2S 2 lways use the lowest ratio of the ions! = MgS Step 3: riss cross; reduce subscripts if necessary a 2+ S 2 a 2 S 2 as 10 The formula for the ionic between s and O 11 The ionic compound between a and N so 2 an Os 2 a 2N 2 s 2O a 3N 2 Os 2 a 2N 3 6

7 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook 12 The ionic compound between l and O 13 What is the ionic compound formed between a and l? l3o2 l2o3 al lo a3l2 l2o2 l2a3 No compound 14 What is the ionic compound formed between P and r? 15 What is the formula for sodium phosphide? P 3r SP3 rp NaP (rp) 2 no ionic compound Na3P NaP3 16 What is the formula for strontium bromide? Srr Srr 2 Sr 2r rsr 2 17 The formula for barium sulfide is a 2 S 2. True False 7

8 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook Naming inary Ionic ompounds inary (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. inary compounds end in " ide." Examples: Nal = sodium chloride KI = potassium iodide Li 2S = lithium sulfide Naming inary Ionic ompounds ations Many cations have the same name as the original, neutral atom. harge formula name +1 H + Hydrogen ion Li + Lithium ion K + Potassium ion s + esium ion g + Silver ion +2 Mg 2+ Magnesium ion a 2+ alcium ion a 2+ arium ion Zn 2+ Zinc ion admium ion d l3+ luminum ion Naming inary Ionic ompounds nions 18 Na 2 S is ll monoatomic anions all end in " ide". The ions that are produced from Group 7 (or 17) elements are called halide ions. Group 15 Group 16 Group 17 Nitride N 3 Oxide O 2 Fluoride F Phosphide P 3 Sulfide S 2 hloride l romide r Iodide I Sodium sulfate Sodium sulfide i sodium sulfide Sulfur nitride 19 The correct name for SrO is. 20 The correct name for l 2 O 3 is. strontium oxide aluminum trioxide strontium hydroxide dialuminum oxide strontium peroxide dialuminum trioxide strontium monoxide aluminum oxide E strontium dioxide E aluminum hydroxide 8

9 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook ations formed by Transition Elements ations Formed by Transition Elements Recall that s block metals have only one possible ionic charge, based on the Octet Rule. However, most transition metals can have more than one ionic charge. For this reason, there is a system for designating each ion. Only common transition metals are shown. Silver and cadmium only form one cation, g + and d 2+ Note the mercury cations. ations formed by Transition Elements We will use the Stock naming system (Roman numerals) to name transition metals. Formula Name u +1 opper (I) ion o +1 obalt (II) ion Fe 2+ Iron (II) ion Mn 2+ Manganese (II) ion lead (II) ion Pb 2+ r 3+ Fe 3+ hromium (III) ion Iron (III) ion Writing Formulas with Transition Metals The charge on the cation is indicated by the Roman numeral, as shown in these examples. Iron (III) oxide: Fe 3+ O 2 Write ion formulas. Fe 3+ O 2 riss cross charges. Fe 2O 3 Reduce if necessary. Tin (IV) oxide Sn 4+ O 2 Write ion formulas. Sn 4+ O 2 riss cross charges. Sn 2O 4 SnO 2 Reduce if necessary. 21 The name of Fel 3 is Formulas with Transition Metals iron chloride iron (II) chloride iron (III) chloride 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, then the total positive cation charge must equal the total negative anion charge. In other words, Total cation charge + Total anion charge = 0 (charge of cation) (# of cations) + (charge of anion) (# of anions) = 0 In the case of Fel 3, we make the following substitutions: (charge of cation) (# of cations) +(charge of anion) (# of anions) = 0 (x) (1) + ( 1) (3) = 0 Thus x = 3 and the cation is Fe 3+ or iron(iii). 9

10 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook Formulas with Transition Metals short cut method is to "uncriss cross" the ions, but you must always double check your ions (or you'll get in trouble!). 22 Which metal is capable of forming more than one cation? Fel 3: Fe 1 l 3 Uncriss cross. Fe 3+ l 1 heck the ions l does form a 1 ion and Fe 3+ is Iron (III) Iron (III) loride ro: r 1 O 1 Uncriss cross. r + O heck the ions O forms a 2 ion and r+ does not exist! (this formula had to be reduced from r 2O 2) romium (II) Oxide E K s a l Sn 23 What is the charge on zirconium ion in ZrO 2 24 The formula for tin (IV) oxide is SnO Sn2O SnO2 SnO 25 The formula for copper (II) sulfide is us 2 26 Which one of the following compounds is copper(i) chloride? us ul u 2 S 2 ul 2 (us) 2 E u 2l u2l2 u3l2 10

11 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook 27 The charge on the cation in the salt Fe 2 O 3 is E 6 polyatomic ion is a group of atoms bonded together that have a charge and acts like a single unit or ion They are not free compounds and are not found free in nature. They are found combined with other ions. Eg: Sulfate = (SO 4 ) 2 Nitrate = (NO 3 ) arbonate = (O 3 ) 2 Polyatomic Ions Use " ( ) " to keep the atoms together. o not change the subscripts inside the "( )" 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 Polyatomic Ions (con't) Polyatomic Ions (con't) Familiarize yourself with the polyatomic ions on your reference sheet e careful of ide, ite, and ate! Note that the suffix does not indicate the actual number of O atoms. l is chloride! Naming Ternary Ionic ompounds Ternary ionic compounds contain three 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 ao 3 = calcium carbonate (in eggshells) Zn( 2H 3O 2) 2 = zinc acetate gno 3 = silver nitrate Na 2SO 3 = sodium sulfite Writing Formulas for Ternary Ionic ompounds Ternary ionic compounds 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 ao 3 Zn( 2H 3O 2) 2 gno 3 Na 2SO 3 11

12 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook Writing Formulas for Ternary Ionic ompounds (con't) To write a formula, the criss cross method can again be used. 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: riss cross; reduce subscripts if necessary Li 1+ PO 4 3 Li 3 (PO 4 ) 1 or simply Li 3 (PO 4 ) Writing Formulas for Ternary Ionic ompounds Example: Write the formula for calcium nitrite. a 2+ (NO 3 ) a(no 3 ) 2 When writing formulas with polyatomic ions, there are two important things to remember: 1) It is helpful to use " ( ) " to keep the atoms together, keeping the charge OUTSIE the ( ) For example nitrate = (NO 3) 1 carbonate = (O 3) 2 2) NEVER alter any symbols or subscripts INSIE inside the "( )" 28 The formula for aluminum phosphate is 29 The formula for magnesium carbonate is l(po 4 ) l 3(PO 4) l2(po4)3 l3(po4)3 Mg 2(O 3) Mg(O3) Mg 2(O 3) 2 Mg(O3)2 30 The formula for calcium sulfate is 31 The formula for sodium hydroxide is a(so 4) a 2(SO 4) 2 a(so 3) a 2(SO 3) 2 Na (OH) 2 Na(OH) Na(OH2) Na(HO) 12

13 Ionic_onding_&_Ionic_ompounds_Presentation_v_1.1.notebook 32 NalO is 33 Mg(HO 3 ) 2 is sodium chlorate Magnesium carbonate sodium chloride sodium chlorite sodium hypochlorite Magnesium hydrogen carbonate Magnesium hydroxide Magnesium carboxide 34 mmonium carbonate is (NH4)(O3) (NH4)2(O3) (NH4)(O3)2 PRTIE Recognizing and Writing Symbols omplete the table by filling in the gaps. (NH4)2(O2) PRTIE Writing Formulas for Ionic ompounds omplete 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. PRTIE Writing Formulas for Ionic ompounds Write the formula for the following compounds: 1. Magnesium iodide 2. alcium sulfite 3. arium hydrogen carbonate 4. Iron (III) phosphate 13

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