Bonding p. 97-106
Jan 16, 2016
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