Ch 5 & 6: Bonding, Formulas and Naming Notes

Types of Chemical Bonds: A. Ionic Bonding 1) Positively charged ions are attracted to negatively charged ions, making a neutral compound. 2) Properties of Ionic Compounds: a) high melting points. b) dissolve in water to form solutions that are good conductors of electricity (electrolytes). c) have a large electronegativity difference between elements. d) usually form between metals and nonmetals.

3) The Octet Rule: a) Atoms tend to gain or lose electrons in order to acquire a full set of valence electrons (stable octet). b) Atoms will transfer electrons (e-) to each other in order to have a full set of valence electrons. c) When electrons are transferred, ionic bonds are formed.

Ions Atoms can form ions by gaining or losing electrons. Metals tend to lose one or more electrons to form positive ions called cations. Cations are generally named by using the name of the parent atom.

Ions Nonmetals tend to gain one or more electrons to form negative ions called anions. Anions are named by using the root of the atom name followed by the suffix –ide.

4) Types of Compounds: a) Binary form from monatomic ions – have 1 cation and 1 anion. Ex) Mg+2 O-2 Ca+2 Cl-1 MgO CaCl2

+ 1 - 2 Not Balanced O -2 O -2 1 x -2 = -2 2 x +1 = +2 Na +1 O -2 Na +1 Na +1 O -2 1 x -2 = -2 2 x +1 = +2 2 + (- 2) = 0 Balanced Na2O

+3 -2 Not Balanced O -2 Al +3 Al +3 O -2 Al +3 O -2 O -2 2 x +3 = +6 3 x -2 = -6 + 6 + (- 6) = 0 Balanced Al2O3

4) Types of Compounds: b) Tertiary form from polyatomic ions which consists of a group of atoms covalently bonded with a single charge that bond ionically with other ions. Ex. “ammonium sulfate” , NH4+1 SO4-2 (NH4)2SO4

X Name this compound: FeO If that’s correct, name this: Fe2O3 How can we distinguish between these compounds? What is the charge on the oxygen in each compound? Then what is the charge on the iron in each compound? Fix the name of the first compound: Iron oxide Iron (II) oxide Fe+2 O-2 Fe+3 O-2 Iron (III) oxide

Ions Ion Charges and the Periodic Table

5) Polyvalent Metals: Some metals including the transition metals do not follow the octet rule and may form more than 1 kind of cation. These ions are named with roman numerals to distinguish between them. Ex) Fe+2 iron (II) read “iron two” Fe+3 iron (III) read “iron three” FeCl2 iron (II) chloride FeCl3 iron (III) chloride Copper (I) sulfate Copper (II) phosphate Cu2SO4 Cu3(PO4)2

6) Lewis Dot Diagrams for elements: # of val. Electrons Dot Diagram Li 1 Li N 5 Be 2 F 7 Ne 8 Au **Note: Only show s and p orbitals in dot diagram.

Electron Dot Diagram for Atoms and Ions

7) Lewis-dot diagram for sodium chloride: [Na+] [ -]

B. Covalent Bonding 1) Covalent Bonds are formed by sharing pairs of electrons between 2 atoms. 2) Usually formed between two nonmetals with a low electronegativity difference. 3) Molecules: a) a group of atoms held together by covalent bonds b) molecular substance – contains molecules

4) Naming: uses prefixes: 1 mono- 4 tetra- 7 hepta- 10 deca- 2 di- 5 penta- 8 octa- 3 tri- 6 hexa- 9 nona- b) end in “ide” c) More electronegative element is written last d) Only use a prefix on the first element if it is more than one. e) Always use a prefix for the second element. Ex) water H2O dihydrogen monoxide smog NO2 nitrogen dioxide

5) Types of formulas for covalent bonding a) Molecular Formula shows how many atoms make up a compound. ex. CH4 & H2O b) Structural Formula shows how the atoms are bonded to each other. ex.

1. Uses 2 dots to show an unshared pair of electrons. 2. Uses dashes to represent covalent bonds (a shared pair of electrons) in a structural formula. 3. The octet rule should be satisfied for each element in the compound. c) Empirical Formula is the lowest whole number ratio of all the elements in the compound. Ex) C6H6 = CH C6H12O6 = CH2O

6) Multiple Bonds – can be used to satisfy the octet rule Single Bonds – Share 1 pair of electrons. Ex) methane or phosphorous trichloride

Double Bonds – Share 2 pairs of electrons. Ex) formaldehyde

Triple Bonds – Share 3 pairs of electrons (strongest bond). Ex) ethyne

8) Properties of Covalent Bonds a) Low melting points, brittle, strong odor, poor conductors of electricity. b) Polar Bonds – form between elements with large differences in electronegativity. These have an uneven sharing of electrons. Ex) water

c) Nonpolar bonds – exert equal pull on the electrons. Ex) O2

9) Electronegativity Chart is used to determine bond type non polar covalent polar covalent ionic bonds 0.4 1.9 4.0 even sharing - no charge uneven sharing – slight charge on molecule electrons transferred – forms ions

C. Ionic & Covalent Bonds Summary: Ionic Bonding Covalent Bonding metal-nonmetal nonmetal-nonmetal e- transferred e- shared large electronegativity difference (>1.9) electronegativity difference (0 1.9) ions formed no ions written cation (+) anion (-) more electronegative element written last name cation - name anion use # prefixes/ends in ide forms ionic compound (formula unit) in a crystal lattice forms molecules Written with a chemical or empirical formula Written with a molecular or structural formula NaCl – sodium chloride CCl4 – carbon tetrachloride

[Na+] [ -]

carbon tetrachloride

D. Acids: 1) A molecular compound that dissolves in water to produce H ions and a characteristic anion. 2) In water, acids behave like ionic compounds. 3) Most acid formulas begin with H. (Except organic acids) “ COOH” 4) The number of hydrogens in the formula depends upon the charge of the anion.

5)Types of Acids a.) Organic Acids contain the carboxylic group, -COOH or Ex) CH3COOH acetic acid (vinegar) (or HC2H3O2)

b.) Binary Acids contain hydrogen and 1 type of anion. A two-word name is used for binary acids. 1st word: prefix is “hydro” root is formed from the anion anion suffix “ide” is changed to “ic” 2nd word: is “acid” Ex) HCl anion is chloride hydrochloric acid Prefix root suffix HBr anion is bromide hydrobromic acid

c.) Oxo (Tertiary) Acids: contain oxygen within a polyatomic ion. A two-word name is used for oxo acids. H2SO4 sulfate sulfuric acid H2SO3 sulfite sulfurous acid sulfur or phosphor (to sound better) 2nd word is “acid” If you “ate” something you don’t like, you say “ic” “ite-ous”

HNO3 anion is nitrate nitric acid root suffix H3PO3 anion is phosphite phosphorous acid Nitrous acid, anion is nitrite formula is: HNO2 Phosphoric acid, anion is phosphate formula is: H3PO4

E. Hydrates: 1.) Ionic compounds that absorb H2O into their solid structures. Ex) magnesium sulfate heptahydrate (epsom salt) Formula: MgSO4  7H2O 2.) Anhydrous substance – substance without water MgSO4 Ex) CuSO4 • 5H2O copper (II) sulfate pentahydrate (bright blue) CuSO4 – anhydrate (light blue/white)