1 - Intro to Chemical Bonding “Bonding” is the process of joining atoms together The Chemical Bond – Force holding atoms together within a substance Intra-molecule bonds create stable water molecules

1 - Intro to Chemical Bonding How many water drops can sit on a coin? Inter-molecule bonds make water molecules “sticky”

1 - Intro to Chemical Bonding Why does bonding occur? Bonding creates a new arrangement of electrons, which is more stable than before. Stable Octet – Arrangement of 8 valence electrons found in Noble gases (2 valence electrons in He) Everything changes in a direction of greater stability!

1 - Intro to Chemical Bonding Electrons are transferred between metallic losers and non-metal gainers in forming salt

Recall that there are two types of elements: Metals (Losers) Chemically weak Low Ionization energy 1, 2, or 3 valence electrons Lose electrons in reactions Na 2-8-1 Aluminum Foil

Recall that there are two types of elements: Nonmetals (Gainers) Chemically Strong High Ionization energy 5, 6, 7 valence electrons gain electrons in reactions Cl 2-8-7 sulfur

Which leads to three types of “substances” formed When a metal combines with a nonmetal The Metal transfers e- to nonmetal forming ions  these are called Ionic compounds Salts Like NaCl

Which leads to three types of “substances” formed When a non-metal combines with a non-metal Two Nonmetals share electrons with one another.  These form Molecules and are called Molecular compounds (and elements) Water H2O

Which leads to three types of “substances” formed When a metal atom is with other metal atoms Metals – Pure or mixed (losers) The lost electrons act to glue the metal ions together These can form be pure metals or Metallic alloys Steel Fe,Cr

Learning check How does one tell? Notice: in compounds Identify each sample as ionic, molecular or metallic. CO2 SrO H2S Cu Al NO3 C6H12O6 NaI How does one tell? Notice: in compounds the 2nd element is a gainer? Is the first element a loser or gainer? Loser = ionic, gainer = molecular Only loser = metallic ex: Cu

Learning Check Identify each sample as ionic, molecular or metallic. CO2 SrO H2S Cu Al NO3 C6H12O6 NaI Nonmetal bonded to nonmetal = molecular Metal bonded to nonmetal = ionic Nonmetal bonded to nonmetal = ? All metal copper atoms = ? metal bonded to nonmetals = ? All nonmetals= ? ?

Section 2A Ionic Bonds Ionic Substances

Ionic Compounds -Made of Ions (Charged “atoms”) Formed when metal atoms transfer electrons to nonmetal atoms Ex: Na atom 2-8-1 - transfers 1 e — to Cl atom 2-8-7 Becomes Na+ ion 2-8 and Cl- ion 2-8-8 Both with 8 valence electrons like noble gases: Stable “octet” Video 4 min

Ionic bond: attraction between oppositely charged ions Ex Na+ and Cl- in salt NaCl Cation – Positively charged metal ion ex: Na 1+ “sodium” ion Anion – Negatively charged nonmetal ion ex: Cl1- chloride” ion Name: Sodium Chloride sodium ions bonded to chloride ions

Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ forms solid crystals with equal positive and negative charges so its neutral Properties: Strong continuous chemical bonds = high melting points (above 3000C) Where Is the Ionic Bond? FYI: Most of these compounds are “salts”

Ionic properties NaCl (aq) Brittle: Like charged ions repel when struck Good electrical conductors when dissolved in water NaCl (aq)

Learning Check In terms of loss or gain of electrons, how do metals and nonmetals behave differently during reactions? Describe the three types of substances formed from metals and nonmetal elements. Most compounds contain “atoms” with how many valence electrons? Explain. In terms of electrons, how do ionic bonds and ionic compounds form? In terms of forces (bonding), why do salts (ionic compounds) have such high melting points? Why are salts brittle?

11. Which type of bond is formed when electrons are transferred from one atom to another? (1) covalent (3) hydrogen (2) ionic (4) metallic 12. Which type of bond is found in sodium bromide? (1) covalent (3) ionic (2) hydrogen (4) metallic 35. Which of the following solids has the highest melting point? (1) H2O(s) (3) SO2(s) (2) Na2O(s) (4) CO2(s)

Ionic Substances Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ “NaCl” is one Formula unit ( “molecule” ) smallest number of ions possible Some are Binary compounds: made of two elements only Ex: MgCl2, magnesium chloride: 1 Mg 2+ with 2 Cl- NOTICE: Positives and negatives balance each other out so compound is neutral Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ No separate molecules

Learning Check: What kind of substance is NaCl? HDYK? 2. Why don’t we say “one molecule of NaCl”? 3. How many Na+ ions would be needed to “neutralize” an O-2 ion? 4. What do you think will be the chemical formula for sodium oxide?

2B Lewis Structures for Ionic

Lewis (Electron Dot) Structures – used to show bonding For Elements and Ions – dots or x’s used to represent valence electrons Atoms hydrogen: H Magnesium: Mg e- configuration: 1 2-8-2 Oxygen: O Chlorine: Cl 2-6 2-8-7

Lewis structures for ions Ex: Ions Losers: hydrogen H Magnesium: Mg Gainers: Oxide: O Chloride: Cl 2+ 1+ [ ]2- [ ]1- x x x

Learning Check: 1. Draw the Lewis electron dot symbols for the following atoms: a. Nitrogen b. potassium c. sulfur d. aluminum 2. Draw the Lewis electron dot symbols for the following ions: a. nitride ion b. potassium ion c. sulfide ion d. aluminum ion

Notice: Most gainer ions will end up with 8 dots; Doesn’t matter what the element is. Can you think of an exception? Hydride- [H:]-1

Lewis structures in bonding For Ionic bonding – Metal atoms pass electrons to nonmetal atoms to reach stable octet (8 val. e-) Ex: NaCl: Na + Cl x x becomes Na+ [ Cl ]1-

Ionic Bonding MgCl2 Mg + Cl Cl becomes Mg 2+ [ Cl ]1- [ Cl ]1- x x x

[ ]2- Practice problems Mg O Mg2+ O x Draw the Lewis e- dot structure for MgO x x Mg O x [ ]2- Mg2+ O

Learning Check: Draw the Lewis electron dot diagrams for the following ionic compounds: KF K2S CaF2

Section 3 Naming and Formula writing Ionic substances

Writing formulas and naming compounds  All compounds are made of two parts a “Loser” ……bonded to a …..“gainer” Ionic compounds formulas = Empirical Formulas – Show the lowest whole number ratio of Ions ex: NaCl Ions combine in ratio to become neutral Ex: MgCl2 : 1 Mg 2+ ion : 2 Cl – ions Ex: NaCl 1 Na : 1 Cl

Writing formulas and naming compounds Ex: MgCl2 : 1 Mg 2+ ion : 2 Cl – ions Naming: named … Magnesium Chloride (negative ions end in ide) Notice: Loser ion (metal first), then gainer ion (nonmetal) Ex: Sodium + oxygen Na1+  + O 2- (need 2 to balance) Na1+  Sodium Oxide Na2O The 2 is the “Subscript” Notice: No reference is made to how many in the name (We don’t say “disodium oxide”)

Writing formulas: Where do you find the charge? Look at the “oxidation state” (the typical charge) Ex: Calcium Chloride Ca+2 Cl-1 Cl-1 CaCl2

Name the following binary compounds: CaBr2 Na2O SrI2 Li3N Practice problems: Name the following binary compounds: CaBr2 Na2O SrI2 Li3N Calcium Bromide Sodium Oxide ? Binary compounds: made of only two elements Notice: no reference is made to how many. What are the subscript numbers? Ratios!

Potassium Oxide Magnesium Iodide Calcium sulfide Aluminum chloride Practice Write the empirical formula for the following compounds (remember to balance the charges!) Potassium Oxide Magnesium Iodide Calcium sulfide Aluminum chloride Aluminum oxide NEVER leave charges on formulas! -2 +1 K2O +1 -2 K2O +2 -1 MgI2 -2 +2 Simplify to lowest ratio Ca2S2 ? ? +3 -1 ? +3 -2 ?

Transitional metals – many with multiple charges Use the “stock” system Roman numerals which represent the charge of the positive ion Transition elements can lose e- from outer and inner sublevels Ex: Cu 1+  “copper one” ion vs. Cu 2+  “copper two” ion Copper(I) Oxide Cu 1+ + O 2- 2 Cu 1+ + O 2- Cu2O Which Copper oxide ?  Cu O Cu = +2 Copper(II) oxide +2 -2

Fe can be +2 or +3 so need to distinguish Ex: Fe2O3 Fe can be +2 or +3 so need to distinguish Slice up into loser and gainer Fe? 2 | O 3 Identify the charge on the gainer Fe? 2 | O 2- 3 Iron(III) oxide +6 3(-2) = -6 2 = +3

Practice problems: name the following +1 -1 Copper (I) iodide 1. Cu I 2. Cu I2 3. Hg O 4. Hg2 I2 +2 -1 Copper (II) iodide ? +2 -2 ? +1 -1 Hg2+2 Mercury “one” ion -2 ___ 2 +2 A “poly-atom-ic” ion

19 Which formula correctly represents the composition of iron (III) oxide? (1) FeO3 (3) Fe3O (2) Fe2O3 (4) Fe3O2

Test your learning Name these: 1. Na2O 2. MgI2 3. PbI4 4. Hg2I2 Write formulas: 1. potassium oxide 2. Calcium nitride 3. Lead (II) iodide 4. Copper (I) sulfide Draw Lewis structures for each #2 above

Polyatomic ions Ternary Compounds are large compound ions that stay together as one unit ex: ammonium NH4+ click on the slide

Polyatomic ions In Ternary Compounds (contain 3 or more elements) ex: NaOH Sodium hydroxide

Polyatomic ions (charged “molecule”) Most Names end in -ate or –ite means its bonded with oxygen. Ex: SO4 2-  called “sulfate” ion As in copper sulfate = CuSO4 SO3 2-  “sulfite” ion NO3 1-  “Nitrate” ion As in potassium nitrate = KNO3 NO2 1-  “Nitrite” ion Notice: -ates have more oxygen and –ites have less.

Two ammonium ions bond for every one carbonate Ex: sodium sulfate Na+  + SO4 2- 2Na+  + SO4 2- Na2SO4 Ex: ammonium Carbonate NH4+ + CO3 2- 2 NH4+ + CO3 2- (NH4)2 CO3 Notice: (NH4) Parentheses are used if more than one ion is represented – subscript comes after Two ammonium ions bond for every one carbonate

Naming Problems 1. Na2CrO4 2. K2Cr2O7 3. (NH4)2S 4. NaOH 5. Ca(OH)2 (most compounds split after the first element) 1. Na2CrO4 2. K2Cr2O7 3. (NH4)2S 4. NaOH 5. Ca(OH)2 6. CaSO4 7. CaSO3

formula problems Write the formulas of these ternary compounds: Magnesium sulfate Aluminum nitrate Copper (II) carbonate Zinc acetate Ammonium chloride -2 +2 -1 +3 ? ? ? -? ? ?

Test your learning Name these: 1. NaC2H3O2 2. Fe(ClO3)2 3. K3PO4 4. SnO2 5. Na2O2 Write the formula: 1. Mercury(II) chlorite 2. Calcium carbonate 3. Ammonium sulfide 4. Lead (II) oxalate 5. Potassium permanganate

Ionic (salts) Molecular Metals