Presentation on theme: "Chapter 8: Basic Concepts of Chemical Bonding Why do TiCl 4 and TiCl 3 have different colors?... different chemical properties?... different physical states?"— Presentation transcript:
Chapter 8: Basic Concepts of Chemical Bonding Why do TiCl 4 and TiCl 3 have different colors?... different chemical properties?... different physical states?
Chemical Bonding and Properties Difference in colors is due to differences in electronic configuration for TiCl 3 and TiCl 4 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
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.
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 NaXeP
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&2
Types of Ions Monatomic ions –Single atom ions O 2- Na + Al 3+ Polyatomic ions –More than one atom ions NH 4 + OH – SO 4 2-
Predicting 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 Elements Note periodicity of charges
Transition 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 Related to position in the periodic table; note exceptions for B, C, N Polyatomic Ions tend to reflect the charge of the base element
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 NaCl NaCl
Why do atoms form bonds? Practice Mg, S Ca, Br Metal Non-Metal
Properties 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
Structure and Properties Why are crystalline solids brittle, whereas metallic solids are malleable?
Structure and Properties Brittleness brittle2.mov maleable2.mov
Examples of Ionic Formulas What is the formula of each of these compounds?
Writing Formulas for Ionic Compounds Crisscross Method Example Ca 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 PracticeLi and O Mg and O Ca and N
Chemical Formulas Remember Combine ions to obtain electrical neutrality Ionic_Formula.exe
Naming Binary Ionic Fixed Charge Compounds (Formula Name) Formula Name Example: Li 2 O 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 CaCl 2 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.
Naming Binary Ionic Compounds STOCK (Transitional Metals) Formula Name CoCl 2 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 (roman numeral) 3.Determine the charge of the anion 4.Balance the charges so the compound is neutral. Ca +2 and Cl –1 CaCl 2 Cu + 2 and O –2 CuO
Naming Ternary Molecular Structures What is a Ternary Molecular Structure? Example MgSO 4 Magnesium Sulfate CuSO 4 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
How do we distinguish between ionic and covalent compounds? What do you notice? Compounds
Why do atoms form bonds? Covalent bond Shared pair of electrons between two atoms. Non-metal and Non-metal
Lewis Structures Lewis StructuresA 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 Cl 2, I 2, F 2, Br 2, O 2, H 2, N 2
Why do atoms form bonds? Characteristics of covalent bonds Single Bonds –Ex. H 2 Double Bonds –Ex. O 2, H 2 CO Triple Bonds –Ex. N 2, C 2 H 2 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 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 Formulas Examples
Structural Formulas A few Models NH 3 CO 2 How are the atoms connected? H 2 SO 4
Lewis Structure for Super 7’s Draw Lewis structures for super 7’s
Chemical Formulas S 8, O 2, O 3 - 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
Naming Binary Covalent Compounds Practice Name Formula What is the formula for the following compounds? 1.Write the chemical formula of the first element listed. 2.Write the prefix number as a subscript. 3.Write the chemical formula of the second element listed. 4.Write the prefix number as a subscript. a.Pentachlorine dioxide b.Carbon monoxide c.Tribromine hexasulfide
Naming Binary Covalent Compounds Practice Formula Name What is the name of the following compounds? 1.Write the number of the first element as a prefix, add the name of chemical. 2.Write the number of the second element as a prefix, add the name of chemical and end in –ide. a.P 4 C 8 b.F 9 I 6 c.SN 3