Ionic Compounds and Metals Chapter 7

Chapter Big Idea Atoms in ionic compounds are held together by chemical bonds formed by the attraction of oppositely charged ions.

Ion Formation Section 1

Section 1: Essential Questions & Vocabulary What holds atoms together in a chemical bond? How do positive and negative ions form? How does ion formation relate to electron configuration? Vocabulary Octet Rule Cation Chemical bond Anion

Section 1: Main Idea Ions form when atoms gain or lose valence electrons to achieve a stable octet electron configuration.

Valence Electrons and Chemical Bonds chemical bond - the force that holds two atoms together Formed by the attraction between the POSITIVE NUCLEUS of one atom and the NEGATIVE ELECTRONS of another atom. Can also be formed by the attraction between positive ions and negative ions. Atom’s try to form the octet—the stable arrangement of eight valence electrons in the outer energy level—by gaining or losing valence electrons.

Positive Ion Formation CATION - A positively charged ion A neutral atom becomes a positively charged ion when it loses one or more valence electrons in order to attain noble gas configuration (octet rule)

Metal Ions Metals are reactive because they lose valence electrons easily. Group 1 and 2 metals are the most reactive Only have to lose 1 or 2 electrons

Transition Metal Ions Transition metals usually have a ns2 outer energy level. Transition metals will usually lose those ns2 electrons first which leads to a 2+ cation formation.

Transition Metal Ions Transition metals commonly form 2+ or 3+ ions, but can form greater than 3+ ions. Pseudo – Noble Gas Configurations – other relatively stable electron arrangements

Some Multiple Oxidation State Elements

Negative Ion Formation ANION - a negatively charged ion. A neutral atom becomes a negatively charged ion when it gains electrons to fill an octet.

Nonmetal Ions Nonmetal gain the number of electrons that, when added to their valence electrons, equals 8. Some nonmetals can gain or lose other numbers of electrons to complete an octet.

Complete Teaching Transparency 22

Ionic Bonds and Ionic Compounds Section 2

Section 2: Essential Questions & Vocabulary How do ionic bonds from and how are the ions arranged in an ionic compound? What can you conclude about the strength of ionic bonds based on the physical properties of ionic compounds? Is ionic bond formation exothermic or endothermic? Vocabulary Compound Crystal lattice Ionic bond Electrolyte Ionic compound Lattice energy

Section 2: Main Idea Oppositely charged ions attract each other, forming electrically neutral ionic compounds.

NaCl NaNO3 Compound COMPOUND more than 2 elements 2 elements Binary Ternary Compound NaCl NaNO3

Formation of the Ionic Bond IONIC BOND - The electrostatic force that holds oppositely charged particles together in an ionic compound. IONIC COMPOUNDS – Compounds that contain ionic bonds. Oxides – ionic bonds occur between metals and nonmetal oxygen. Most other ionic compounds are called salts.

Binary Ionic Compounds Binary Ionic Compounds – contain only two different elements. A metallic cation and a nonmetal anion

Compound Formation

Compound Formation

Compound Formation: Practice Sodium and Nitrogen Strontium and Fluorine Lithium and Oxygen Aluminum and Sulfur Compound Formation: Practice

Compound Formation: Practice Solutions Sodium and Nitrogen Strontium and Fluorine Lithium and Oxygen Aluminum and Sulfur Compound Formation: Practice Solutions

Properties of Ionic Compounds The chemical bonds in a compound determine many of its properties. Physical Structure – Ionic Crystals Ratio of cations to anions is determined by the number of electrons transferred from the metal to the nonmetal atom. Ions are packed in a repeating pattern that balance the forces of attraction and repulsion

Physical Structure of Ionic Compounds Crystal Lattice – a three-dimensional geometric arrangement of particles responsible for the structure of many minerals. Result from the strong attractions among the positive and negative ions

Physical Properties of Ionic Compounds Because the attraction force between ions is high, ionic compounds tend to have high melting points, high boiling points and have hard surfaces. Mostly solid at room temperature.

Properties of Ionic Compounds: Conductivity Conductivity - depends on availability of charged particles to move freely. Electrolyte – ionic compound whose aqueous solution conducts electric current. Ions in Solid State Ions in Liquid State Ions fixed (cannot move) Do not conduct electricity Ions can move Excellent conductors of electricity

Properties of Ionic Compounds: Hardness Ionic compounds are hard, rigid, brittle solids due to the strong attractive forces that hold the ions in place.

Energy and the Ionic Bond In all chemical reactions, energy is either absorbed or released. Endothermic – reactions that absorb energy Exothermic – reactions that release energy Formation of ionic compounds is always exothermic. Reaction gets warmer (energy released as heat).

Lattice Energy Mini Activity How does interionic radius affect lattice energy? How does lattice energy affect physical properties of ionic compounds? Procedure: 1. Look up the melting point of each compound listed. 2. Create a graph showing the relationship between ionic size and lattice energy. 3. Create a graph showing the relationship between lattice energy and melting point.

Lattice Energy The amount of energy required to separate 1 mol of the ions of an ionic compound Reflects the strength of the forces holding the ion in place Related to size of the ions bonded. Smaller ions – stronger attraction force and thus, higher lattice energy. Larger ions – weaker attraction force and thus, lower lattice energy.

Complete Teaching Transparency 23 – Ionic Bonds

Names and Formulas for Ionic Compounds Section 3

Section 3: Essential Questions and Vocabulary What is a formula unit and how does it relate to an ionic compound’s composition? How do you write the formulas for compounds formed from different ions and oxyanions? What are the naming conventions for ionic compounds and oxyanions? Vocabulary Nonmetal Polyatomic ion Formula unit oxyanion Monoatomic ion

Section 3: Main Idea In written names and formulas for ionic compounds, the cation appears first, followed by the anion.

CHEMICAL FORMULA NaCl CO2 IONIC COVALENT Formula Unit Molecular

Formulas for Ionic Compounds Formula unit – represents the simplest ratio of the ions involved When writing names and formulas for ionic compounds, the cation appears first followed by the anion. Mg+2 and Cl- ions exist in a 1 to 2 ratio. Overall charge of formula unit is zero because it represents the crystal lattice which is neutral. Magnesium Chloride Standardized system for naming compounds so that chemists around the world can communicate with one another Given a chemical name – write the chemical formula Given the chemical formula – write the chemical name

Monoatomic Ions & Oxidation Number Oxidation state – the charge of a monatomic ion. equal to the number of electrons transferred from the atom to form the ion. Monoatomic Ions – one atom ions

Formulas for Binary Ionic Compounds Rules for writing chemical formulas for binary ionic compounds: The symbol for the cation is always written first, followed by the symbol of the anion. Subscripts represent the number of ions of each element in an ionic compound. If no subscript is written, then it represents 1. The total charge must equal zero in an ionic compound.

Formula for Binary Ionic Compound Determine the formula for the ionic compound formed from potassium and oxygen. K+ O2- K2O

Formula for Binary Ionic Compound: Practice Determine the formula for the compound formed from aluminum ions and sulfide ions. Al3+ S2- Al2S3

Formula for Polyatomic Ionic Compounds Polyatomic ions – ions made up of more than one atom. Polyatomic ions exist as a unit!!! NEVER change subscripts of the atoms within the polyatomic ion. If more than one polyatomic ion is needed, place parentheses around the ion and write the appropriate subscript outside the parentheses.

Common Polyatomic Ions

Formula for a Polyatomic Ionic Compound A compound formed by calcium ions and phosphate ions is often used in fertilizers. What is the formula unit? Ca2+ PO43- Ca2+ PO43- Ca3(PO4)2

Formula for a Polyatomic Ionic Compound: Practice Sodium and nitrate Calcium and chlorate Aluminum and carbonate

Formula for a Polyatomic Ionic Compound: Practice Solutions Sodium and nitrate Calcium and chlorate Aluminum and carbonate Al2(CO3)3

Complete Math Skills Transparency 8 Common Polyatomic Ions Ion Name NH4 ammonium IO4 periodate NO2 nitrite C2H3O2 acetate NO3 nitrate H2PO4 dihydrogen phosphate HSO4 hydrogen sulfate CO32 carbonate OH hydroxide SO32 sulfite CN cyanide SO42 sulfate MnO4 permanganate S2O32 thiosulfate HCO3 hydrogen carbonate O22 peroxide ClO hypochlorite CrO42 chromate ClO2 chlorite Cr2O72 dichromate ClO3 chlorate HPO42 hydrogen phosphate ClO4 perchlorate PO43 phosphate BrO3 bromate AsO43 arsenate IO3 iodate  

Names for Ions and Ionic Compounds Oxyanion - a polyatomic ion composed of an element (usually a non-metal), bonded to one or more oxygen atoms.

Names for Ions and Ionic Compounds The oxyanion with the greatest number of oxygen atoms is named using the prefix per-, the root of the nonmetal, and the suffix –ate. The oxyanion with one fewer oxygen atom is named using the root of the nonmetal and the suffix –ate. perchlorate chlorate

Names for Ions and Ionic Compounds The oxyanion with two fewer oxygen atoms is named using the root of the nonmetal and the suffix –ite. The oxyanion with three fewer oxygen atoms is named using prefix hypo-, the root of the nonmetal, and the suffix –ite. chlorite hypochlorite

Names for Ions and Ionic Compounds Chemical nomenclature is a systematic way of naming compounds. Name the cation followed by the anion. For monatomic cations use the element name. For monatomic anions, use the root element name and the suffix –ide. To distinguish between different oxidation states of the same element, the oxidation state is written in parentheses after the name of the cation. When the compound contains a polyatomic ion, name the cation followed by the name of the polyatomic ion.

Names for Ions and Ionic Compounds

Complete Teaching Transparency 24 – Formulas of Ionic Compounds

Metallic Bonds and the Properties of Metals Section 4

Section 4: Essential Questions & Vocabulary What are the characteristics of a metallic bond? How does the electron sea model account for the physical properties of metals? What are alloys, and how can they be categorized? Vocabulary Physical property Metallic bond Electron sea model Alloy Delocalized electron

Section 4: Main Idea Metals form crystal lattices and can be modeled as cations surrounded a “sea” of freely moving valence electrons.

Metallic Bonds Metals are not ions but do share some properties with ionic compounds. Why??? Both bonds focus on the attraction of particles with unlike charges. Metals form lattices in their solid state. 8 to 12 other atoms closely surround each metal atom. Outer energy levels of metal atoms overlap

A Sea of Electrons The electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electrons. Delocalized electrons – the “sea of electrons” that are free to move around forming a metallic cation. metallic bond – the attraction of an metallic cation to the delocalized electrons.

Video on Metallic Bonding Analogy

Video on Metals & Metallic Bonding

Properties of Metals: Melting & Boiling Points Melting points of metals vary greatly but generally are high. Mercury – Liquid at room temperature Tungsten – 3422 ⁰C Why the large difference in melting and boiling points?

Properties of Metals: Melting & Boiling Points Melting Point Boiling Point Melting points are not extreme because the cations and electrons are mobile in an atom. Boiling points are much higher because during boiling, atoms must be separated from the group of cations and electrons requiring much more energy.

Properties of Metals: Malleability & Ductility Malleable – ability to be hammered into sheets. Ductile – ability to be drawn into wires.

Properties of Metals: Conductivity Mobile electrons surrounding positively charged nuclei make metals good conductors of electricity and heat. The delocalized electrons also interact with light, creating their luster.

Properties of Metal: Hardness & Strength As the number of delocalized electrons increases, so does hardness and strength. Transition metals also have the inner d electrons increasing the total number of delocalized electrons. Transition metals are harder than alkali metals. Titanium Iron

Metal Alloys Alloy – a mixture of elements that has metallic properties. Examples: Stainless steel, brass, cast iron The properties of alloys differ from the elements they contain. Example: Steel is iron mixed with at least one other element. Some properties of iron are present, like magnetism, but steel is stronger than iron.

Types of Alloys Substitutional alloys – formed when some atoms in the original metallic solid are replaced by other metals of similar atomic structure. Interstitial alloys – formed when small holes in a metallic crystal are filled with smaller atoms.

Complete Teaching Transparency 25: Metallic Bonding