Bondingp. 97-106

• chemical bond: interaction between atoms or ions– decreases the potential energy of

an atom; makes it more stable– only the valence electrons are

involved!

Three Types of Bonds

• Bond type depends on electronegativity (electron affinity)– IONIC ： very different

electronegativities•one metal, one non-metal

– COVALENT: both very high•two non-metals

– METALLIC: both low•one or more metals

Review of Ionisation+1

+2 -1-2-3

Metals

Non-metals

Cations

Anions

What kind of bond?

• Na and Cl• O and F• K and Br• Au and Ag• H and O• Mg and F• S and Cl• Ni and Cu

• Ionic• Covalent• Ionic• Metallic• Covalent• Ionic• Covalent• Metallic

Ionic Bonds

• metal (low electroneg., cation) + non-metal (high electroneg., anion)

• Array of positively and negatively charged ions– held together by electrostatic

attraction

• metal loses e- = cation– group 1 (+1) and group 2 (+2)– transition metals (+2 most

common)

• non-metal gains e- = anion– groups 17, 16, 15…

• List, p. 100

sodium and chlorine

• sodium transfers its electron to chlorine

Na Cl

Crystal Lattice (Array)

• structure of an ionic bond• each anion is surrounded by

cations and vice versa

Writing Formulae for Ionic Compounds

• chemical formula: shorthand for elements, ions and compounds

• Ratio of the number of atoms of each element– MgCl2

– C6H12O6

• Ions of opposite charges are attracted to one another.

• Mg2+ Cl-

• MgCl2

• Ions bond because they are electrically attracted to one another– “Opposites attract”

• Polyatomic ions: most covalently bonded, but have an overall electronic charge

• Hand out list: memorize it.

Ionic or Covalent?

• NaCl

• NO2

• N2Br

• NaI• CaS

Ionic or Covalent?

• KNO3

• Fe(CrO4)2

• Cu(OH)2

• BaI

• F2

Ionic or Covalent?

• O2

• AgCl

• AgNO3

Ionic or Covalent?

• NO2

• CO2

• PCl5

• P2S4

• NO3

Writing Formulae forIonic Compounds

• Write the symbols and their charges

• “Cross” the charges to the other side

• Use the charges, without + or – as subscripts

Polyatomic Ions to Memorize

• Ammonium• Nitrite• Nitrate• Sulfite• Sulfate• Hydroxide• Phosphite• phosphate

• Carbonate• Chlorite• Chlorate• Chromate

Naming Ionic Compounds

Naming Cations

• Same as the element!!

Naming Anions

• Ending changes to “ide”• O oxygen oxide• F fluorine fluoride• S sulfur sulfide• Cl chlorine chloride• Br bromine bromide• I iodine iodide

• Chlorine• Iodine• Oxygen• Sulfur• Bromine• Fluorine

• Chloride• Iodide• Oxide• Sulfide• Bromide• Fluoride

Naming Ionic Compounds

• Cation + Anion (“ide” ending)• NaCl sodium chloride• KBr potassium bromide

Naming Ionic Compounds – Type I

• One positively charged ion and one negatively charged ion.

• NaCl– Sodium chloride

• SrF2

– Strontium fluoride

1. CsBr2. MgO3. KF4. AlCl3

5. LiH6. calcium iodide7. rubidium sulfide

1. cesium bromide2. magnesium

oxide3. potassium

fluoride4. aluminum

chloride5. lithium hydride6. CaI2

7. Rb2S

• LiI• CaS• AgBr

• ZnCl2

• Na2S

• barium fluoride• silver oxide

• lithium iodide• calcium

sulfide• silver

bromide• zinc chloride• sodium

sulfide

• BaF2

• Ag2O

Stock system

• Some elements make ions with different charges (p. 100)– “oxidation states”

• Fe2+ Fe3+

• iron(II) iron(III)• Roman numerals

Elements that use theStock System

• These elements have more than one “oxidation state”– Fe (2+, 3+) Cr (2+, 3+)– Cu (1+, 2+) Mn (2+, 3+)– Co (2+, 3+) Pb (2+, 4+)– Sn (2+, 4+)– Hg2+ (mercury II), Hg22+ (mercury I)– Zumdahl, p. 65

Ions to memorize

• Al3+

• Zn2+

• Ag+

• Cd2+

1. CuCl2. SnO3. Fe2O3

4. MnO2

5. PbCl2

6. copper (III) oxide7. vanadium (IV) fluoride

• copper (I) chloride• tin (II) oxide• iron (III) oxide• manganese (IV)

oxide• lead (II) chloride

• Cu2O3

• VF4

1. CoBr2

2. CrCl3

3. CaCl2

4. Al2O3

5. SnBr4

6. Cu2S

7. iron (II) fluoride8. tin (II) oxide

• cobalt (II) bromide• chromium (III) chloride• calcium chloride• aluminum oxide• tin (IV) bromide• copper (I) sulfide

• FeF2

• SnO

• Fe(NO3)3

– Iron(III) nitrate

• Fe2(SO4)3

– iron(III) sulfate

Polyatomic Ion

Ionic Compounds with Polyatomic Ions

• NH4+

– ammonium

• NO3-

– nitrate

1. Na2SO4

2. KH2PO4

3. Fe(NO3)3

4. Mn(OH)2

5. Na2SO3

6. Rb2CO3

7. Mg(HCO3)2

1. sodium sulfate2. potassium dihydrogen

phosphate

3. iron (III) nitrate4. manganese (II)

hydroxide5. sodium sulfite6. rubidium carbonate7. magnesium

bicarbonate

Name Ionic Compounds• KNO3

• Mg(OH)2

• LiCrO4

• Fe(OH)3

• Co(NO3)2

• Mn3(PO3)2

• potassium nitrate• magnesium hydroxide• lithium chromate• iron (III) hydroxide• cobalt nitrate• Manganese (II) posphite

• potassium nitrate• magnesium hydroxide• lithium chromate• iron (III) hydroxide• cobalt nitrate• Manganese (II) posphite

Homework1. CaO2. lithium sulfide3. CrCO3

4. silver iodide5. Cu2SO3

6. calcium phosphate

7. SrI2

8. iron (III) bromide

9. FeBr2

10.cobalt (II) iodide

11.SnO2

12.ammonium nitrate

13.Ag2S

Covalent Bonding

Covalent Bonding

• two or more non-metals• atoms share some valence

electrons (not transfer)• single covalent bond: shares one

pair of electrons• double: 2 pairs of e-

• triple: 3 pairs of e-

• usually each atom donates (shares) one of each pair of electrons

• dative covalent bond: sometimes one atom donates both electrons

F FElectron PairElectron Pair

Shared by both atomsShared by both atomsEach e- donate by each atomEach e- donate by each atom

• number of bonds formed depends on the number of e- required to fill the valence shell– noble gases = full valence, rarely

form compounds

• octet rule: usually, atoms want 8 valence e- (H, He need 2)

• Ex: C has 4 valence e-– needs 4 more to form a full octet– C forms 4 bonds

• Ex: F has 7 valence e-– needs 1 more to form a full octet– F makes one bond

• Nitrogen?

Bonding between C and F

F

F

F

F C

structural hybrid Lewis

formula diagram diagram

=e- pair F e- C e-

=covalent bond

F

F

F

F CF

F

F

F C

Double Bond

• sharing two pairs of electrons• bonds more strongly than a single

bond

• structural hybrid Lewis

CO O CO OCO O

Triple Bond

• Strongest

NN NN NN

Length and Strength of Bonds

single double triple

longest shortest

lowest energy highest energy

Drawing molecule diagrams

1. Decide how many bonds each atom makes.

2. The central atom is the one that makes the most bonds.

3. Draw with single bonds4. Calculate remaining electrons5. Use remaining electrons

• HCN (hydrogen cyanide) – C=4, N=3, H=1

• HCO2- (methanoate ion)

– H=1, C=4, O=2

Draw structural, hybrid and Lewis structures

• HF

• NH3

• CH4

• CF4

• NO2-

• CHCl3

• NH4+

• H2CO

• SeF2

Naming Covalent Compounds

• Ex: CO2

– carbon dioxide• Prefixes

– mono 1– di 2– tri 3– tetra 4– penta 5– hexa 6

1. N2O

2. NO3. NO2

4. N2O3

5. N2O4

6. N2O5

1. Phosphorus pentachloride

2. Phosphorus trichloride3. Sulfur hexafluoride4. Sulfur trioxide5. Sulfur dioxide6. Carbon dioxide

1. Phosphorus pentachloride

2. Phosphorus trichloride3. Sulfur hexafluoride4. Sulfur trioxide5. Sulfur dioxide6. Carbon dioxide

• P4O10

• Fe2O3

• Li2O2

• Mg(NO3)2

• CCl4

• tetraphosphorus decoxide

• iron (III) oxide• lithium peroxide• Magnesium nitrate• Carbon tetrachloride

• tetraphosphorus decoxide

• iron (III) oxide• lithium peroxide• Magnesium nitrate• Carbon tetrachloride

Homework

• NI3 phosphorus trichloride

• SF2 dinitrogen tetrafluoride

• N2O4 sulfur dioxide

• ICl3 diphosphorus pentasulfide

• SF6 dihydrogen monoxide