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Warm-up How many valence electrons does each of the following atoms have? Draw a Bohr Diagram for each element 1. B 2. F 3. Ar 4. Se 5. Ba 6. Si
Warm-upHow many valence electrons does each of the following atoms have? Draw a Bohr Diagram
for each element
1. B
2. F
3. Ar
4. Se
5. Ba
6. Si
Chapter 8: Basic Concepts of Chemical Bonding
Chapter 8: Basic Concepts of Chemical Bonding
• Why do TiCl4 and TiCl3 have different colors? ... different chemical properties? ... different physical states?
Chemical Bonding and Properties
• Difference in colors is due to differences in electronic configuration for TiCl3 and TiCl4
• Differences in chemical behavior are due to differences in the types of bonds
• Bond: forces that hold atoms together in molecules or ionic compounds.
Chemical Bonding• Types of bonds and types of substances
– Ionic
– Covalent
– Metallic
• The type of bond between atoms is partially responsible for the properties of the substance.
Why do atoms form bonds?
Draw orbital diagrams for each of the following elements• Ne
• Na
• Cl
• H
• O
Notes handout
Why do atoms form bonds?• Octet Rule
• Lewis Dot Diagrams
• Atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons.
• Used to illustrate an atoms valence electrons
• Used to illustrate how electrons rearrange during chemical reactions
Lewis Symbols and the Octet Rule
Lewis Symbols and the Octet Rule• Lewis Symbols:
The number of valence electrons available for bonding are indicated by unpaired dots.
Lewis Symbols
• These symbols are called Lewis symbols.
• We generally place the electrons on four sides of a square around the element symbol.
Lewis_symb.exe.lnk
Why do atoms form bonds?• Octet Rule
• Lewis Dot Diagrams
• Atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons.
• Used to illustrate an atoms valence electrons
• Used to illustrate how electrons rearrange during chemical reactions
Na Xe P
Lewis Dot Practice
• O
• Te
• Ca
• Ba
• Ne
• I
• Cs
Ions and Ionic Compounds
• Ions are formed by adding or subtracting electrons from a neutral atom or molecule.
• Cation: positive charge (remove electrons) Na+
• Anion: negative charge (add electrons) Cl-
• Ions may be monatomic or polyatomic
03m07an1&203m07an1&2
Types of Ions• Monatomic ions
– Single atom ions• O 2-
• Na+
• Al3+
• Polyatomic ions– More than one atom ions
• NH4 +
• OH –
• SO4 2-
Predicting Ionic ChargesPredicting Ionic Charges
• Electron Counts of Stable Ions– Ions tend to have the same number of
electrons as the nearest noble gas.• Main group ions of a given element tend to
be different by two units of charge.• Transition metals are not as predictable, but
+2 and +3 are common.
ion_charges.exe
Main Group ElementsMain Group Elements
Note periodicity of charges
Transition ElementsTransition Elements• Not periodic; +2 and +3 common
• Oxoanions generally have the same charge as the simple anion of the same nonmetal.
Charges and Formulas of Oxoanions
Charges and Formulas of Oxoanions
Related to position in the periodic table; note exceptions for B, C, N
Polyatomic Ions
tend to reflectthe charge of the base element
Practice on Ionic Charges
• Pair Share: What is the common charge of an ion of potassium, K?
• Pair Share: What is the common charge of an ion of sulfur, S?
• Pair Share: What is the common charge of an ion of iron, Fe?
Why do atoms form bonds?• Ionic bond
• Example– Lewis Dot
diagram
• A positively charged ion is attracted to a negatively charged ion.
• A transfer of electrons• Metal and a Non-Metal
• NaCl
Na Cl Na Cl
Why do atoms form bonds?
• Practice
• Mg, S
• Ca, Br
Metal Non-Metal
What holds Ionic bonds together?
Formation of an Ionic Compound
Vd02_007.mov
Properties of Ionic BondsProperties of Ionic Bonds
• Ionic bonds are very strong, so separating ions requires much energy
• High melting points, boiling points• Crystals are hard and brittle• Electrical insulators when solid, electrical
conductors when molten or dissolved in water
• Demo:electric_pickle.mov
Electrical ConductivityElectrical Conductivity
Solid NaCl Liquid NaCl
03s11vd103s11vd1
Structure and PropertiesStructure and Properties
• Why are crystalline solids brittle, whereas metallic solids are malleable?
Structure and PropertiesStructure and PropertiesBrittleness
brittle2.mov
maleable2.mov
Examples of Ionic FormulasExamples of Ionic Formulas
• What is the formula of each of these compounds?
Writing Formulas for Ionic Compounds
• Crisscross Method
• ExampleCa and F
• Write the element symbols for the cation and anion, with the cation on the left and the anion on the right.
• Write each ion’s charge as a superscript.
• Crisscross the two charges moving them downward diagonally from one superscript to the other subscript.
Writing Formulas for Ionic Compounds
• Practice • Li and O
• Mg and O
• Ca and N
Practice
• Rewrite these incomplete formulas as correct formulas. AlS CaP BaBr
• Make formulas from the following ions:
Fe2+, PO43- Sc3+, O2-
Bonding with a partner
• You will receive a card with an ion.
• You will find another person with the opposite charge from you.
• You will write the ions on your paper and the formula they will create together.
• Exchange cards and repeat the steps again until you fill up your paper.
Chemical FormulasChemical Formulas
• Remember • Combine ions to obtain electrical neutrality
Ionic_Formula.exeIonic_Formula.exe
Naming Binary Ionic Fixed Charge Compounds
(Formula Name)
Formula Name
Example:
Li2O
1. Name the cation
2. Name the anion, changing the ending to ide
Lithium Oxygen + ide
Lithium Oxide
Naming Binary Ionic Compounds
Name Formula
Example:
Calcium Chloride
Ca +2 and Cl -1
CaCl2
1. Identify the ions involved
2. List the cation first and then the anion
3. Determine that charge of each ion involved
4. Balance the charges so the compound is neutral.
Practice
Write the structural formula for the following:
Hint: separate them into ions and then criss cross
Magnesium phosphide
Calcium iodide
Beryllium oxide
Naming Binary Ionic Compounds STOCK (Transitional Metals)
Formula Name
CoCl2
Example:
Cobalt II chloride
1. Name the cation
2. Determine the charge of the anion
3. Based on the anion, what charge does the cation need to make the compound neutral.
4. Write the cation charge in parenthesis as a roman numeral
5. Name the anion.
Naming Binary Ionic Compounds Stock (Name Formula)
Name Formula
Example:
Calcium Chloride
Copper(II) Oxide
1. List the cation first and then the anion
2. Give the cation the charge stated in the name
3. Determine the charge of the anion
4. Balance the charges so the compound is neutral.
Ca +2 and Cl –1 CaCl2
Cu + 2 and O –2 CuO
Practice
• Writing Formulas “Transition Metals (stock Method)” wksheet
Naming Ternary Molecular Structures
What is a Ternary Molecular Structure?
Example•MgSO4
Magnesium Sulfate
•CuSO4 Copper (II) Sulfate
•A molecule that has more than two elements.•A combination of a metal and a polyatomic ion.•Same rules as Binary Ionic/Stock but just name the polyatomic
Rally Table
• NaF
• K2CO3
• MgCl2
• Be(OH)2
Practice Worksheet
Brain Teaser
• Write the formula for the following elements: Potassium and Phosphorus
• Name the following compounds
• SrS
• Cu2S
• Iron (II) oxide
• Lithium cyanide
• How do we distinguish between ionic and covalent compounds?
• What do you notice?
CompoundsCompounds
Nacl.pdb Ch4.pdb
Why do atoms form bonds?
• Covalent bond
• Shared pair of electrons between two atoms.
• Non-metal and Non-metal
Lewis Structures
• Lewis Structures A representation of a molecule that shows
how the valence electrons are arranged among
the atoms in the molecule
* G. N. Lewis
• Lewis Dot Examples
Why do atoms form bonds?
• Molecule
• Diatomic Molecules
• Super 7
• A group of atoms united by a covalent bond
• A few elements only exist as a pair of atoms never as a single lone atom
• Cl2, I2, F2, Br2, O2, H2, N2
Round Table – Covalent Bonding
• SiH4
• NH41+
• H2Se
• HCl
• HF
• *SO42-
Why do atoms form bonds?• Characteristics
of covalent bonds
• Single Bonds– Ex. H2
• Double Bonds– Ex. O2, H2CO
• Triple Bonds– Ex. N2, C2H2
• Can form multiple bonds satisfy the octet rule
• Two atoms share exactly one pair of electrons.
• Two pairs of electrons shared between two atoms.
• Three pairs of electrons are shared between atoms
Properties of Covalent BondsProperties of Covalent Bonds
• Solids are usually soft
• low melting points
• low boiling points
• Properties arise because molecules are not strongly held together
• Usually found with nonmetals
Structural Formulas
• Why do atoms form bonds?
• Specifies which atoms are bonded to each other
• Distinguish the difference between substances with the same molecular formula
• See models of different types: Why do we have different types of models?
Structural FormulasExamples
Structural Formulas
• A few Models
NH3
CO2
• How are the atoms connected?H2SO4
Co2.pdb
H2so4.pdb
Nh3.pdb
Lewis Structure for Super 7’s
• Draw Lewis structures for super 7’s
Worksheet:
• Draw Lewis Dot structures for the following molecules
Chemical FormulasChemical Formulas
• S8, O2, O3 - What formulas do we find for elements? Elements with different formulas are called allotropes.
• How many atoms make a molecule? Is there any pattern?
xenon oxygen phosphorus sulfur ozone
nonmetals.exe.lnk
Brain Teaser
• Write the Lewis structure for each of the following simple molecules.
• H2S
• C2H4
• SiF4
Shapes Lab• Work with a partner
• Draw the Lewis Dot Diagrams for each of the compounds
• Build each of the compounds using the model kits.
• Sketch the shape of the model– Remember all the holes (bonding sites) of each
atom must be filled in order for it to satisfy the octet rule.
Shapes of Molecules
VSEPR Theory
• Valence Shell Electron Pair Repulsion
• System for predicting molecular shape based on the idea that pairs of electrons orient themselves as far apart as possible.
Shapes of Molecules
How to use VSEPR theory• Total Electron Pairs
– # of Shared and unshared pairs
• Shared Electron Pairs– # of Pairs involved in
covalent bonding• Unshared electron Pairs
– # of Lone pairs of electron• Shape or Geometry
– Linear, bent, trigonal planar, tetrahedral
Examples• HBr
• H2O
• PH3
Shapes of Molecules
What do we do with multiple bonds?
Count the sides of the central atom that have bonds on them
Examples• N2
• HCN
• H2CO
Practice
• Shapes of molecules
THE PASS IT GAME!!
• You will have one paper for each row.• Your job is to do one section and then pass it to
the next person.• There are three sections: Electron dot, molecular
drawing and VSEPR name & angle• Once the last person is done raise your hand and
get a stamp if all is correct.• 1st team will get a prize for each Pass it game!
CCl4
SeO3
BeF2
Polarity of Molecules
Electronegativity
Polar Covalent Bonds
Polar Molecule
– Ex. H2O
• Ability to attract electrons
• Difference in electronegativity tells us who wants the electrons more.
• Atoms do not share electrons evenly.
• Atoms with greater electronegativity have a slight negative charge.
• A molecule is polar if the charge is not evenly distributed
Polarity of Molecules
What would make a Non-Polar Covalent Bond?
– Examples• F2
• PH3
• If the 2 atoms have similar electronegativities.
• The atoms involved exert similar pull on the electrons.
Bond Types and Elctronegativity
Electronegativity Difference
Bond Type
< 0.4 Non- polar covalent
Between 0.5 and 1.9 Polar covalent
> 2.0 Ionic
Polarity of Molecules
• Other side of shapes
• Draw each molecule in its correct VSEPR shape.
PropertiesIonic vs. Covalent
Rally Table - Types of chemical bonds
Covalent Compounds
Naming Binary Covalent Compounds
Covalent compound
Definition
• Non-metal and non-metal• Share Electrons• Nonpolar and polar molecules
Naming Binary Covalent Compounds
Prefixes 1= mono
2= di
3 = tri
4 = tetra
5 = penta
6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deca
Examples:
• Naming water
H2O
• Carbon Dioxide
Activity
• Write the names of
• CCl4
• CO
• SO2
• NF3
*___________________
*___________________
*___________________
*___________________
Naming Binary Covalent Compounds
Practice
Name FormulaWhat is the formula for the
following compounds?
a. Pentachlorine dioxide
b. Carbon monoxide
c. Tribromine hexasulfide
Practice
• Naming Covalent Compounds worksheet
