Chapter 7: Ionic Compounds and Metals. CHEMISTRY Matter and Change

Chapter 7: Ionic Compounds and Metals.

Chapter 7: Ionic Compounds and Metals.

CHEMISTRY Matter and Change

Section 7.1 Ion Formation

Section 7.2 Ionic Bonds and Ionic Compounds

Section 7.3 Names and Formulas for Ionic Compounds

Section 7.4 Metallic Bonds and the Properties of Metals

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Table Of ContentsCHAPTER

7

• Define a chemical bond. octet rule: atoms tend to gain, lose, or share electrons in order to acquire eight valence electrons

chemical bond

cation

anion

• Describe the formation of positive and negative ions.

• Relate ion formation to electron configuration.

Ions are formed when atoms gain or lose valence electrons to achieve a stable octet electron configuration.

Ion FormationSECTION7.1

Valence Electrons and Chemical Bonds

• A chemical bond *

• Chemical bonds form by the attraction between the positive nucleus of one atom and the negative electrons of another atom.


Valence Electrons and Chemical Bonds (cont.)

• 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

• * is called a cation.

• This figure illustrates how sodium loses one valence electron to become a sodium cation.


Positive Ion Formation (cont.)

• Metals are reactive because they lose valence electrons easily.


Positive Ion Formation (cont.)

• Transition metals commonly form 2+ or 3+ ions, but can form greater than 3+ ions.

• Other relatively stable electron arrangements are referred to as pseudo-noble gas configurations.


Negative Ion Formation

• An anion is a negatively charged ion.

• The figure shown here illustrates chlorine gaining an electron to become a chlorine ion.


Negative Ion Formation (cont.)

• Nonmetal ions gain the number of electrons required to fill an octet.

• Some nonmetals can gain or lose electrons to complete an octet.


• Describe the formation of ionic bonds and the structure of ionic compounds.

compound: a chemical combination of two or more different elements

• Generalize about the strength of ionic bonds based on the physical properties of ionic compounds.

• Categorize ionic bond formation as exothermic or endothermic.

SECTION7.2

Ionic Bonds and Ionic Compounds

ionic bond

ionic compound

crystal lattice

electrolyte

lattice energy

Oppositely charged ions attract each other, forming electrically neutral ionic compounds.

SECTION7.2


Formation of an Ionic Bond• * is called an ionic bond.

• * are called ionic compounds.

• Binary ionic compounds contain only two different elements—a metallic cation and a nonmetallic anion.

SECTION7.2


Formation of an Ionic Bond (cont.)

SECTION7.2


Properties of Ionic Compounds

• Positive and negative ions exist in a ratio determined by the number of electrons transferred from the metal atom to the non-metal atom.

• The repeating pattern of particle packing in an ionic compound is called an ionic crystal.

SECTION7.2


Properties of Ionic Compounds (cont.)

• The strong attractions among the positive and negative ions result in the formation of the crystal lattice.

• A crystal lattice is the *.

SECTION7.2



• Melting point, boiling point, and hardness depend on the strength of the attraction.

SECTION7.2


• In a solid, ions are locked into position and electrons cannot flow freely—solid ions are poor conductors of electricity.

• Liquid ions or ions in aqueous solution have electrons that are free to move, so they conduct electricity easily.

• * is an electrolyte.

SECTION7.2




• This figure demonstrates how and why crystals break when an external force is applied.

SECTION7.2


Energy and the Ionic Bond

• Reactions that absorb energy are endothermic.

• Reactions that release energy are exothermic.

SECTION7.2


Energy and the Ionic Bond (cont.)

• * is referred to as the lattice energy.

• Lattice energy is directly related to the size of the ions that are bonded.

SECTION7.2



• Smaller ions form compounds with more closely spaced ionic charges, and require more energy to separate.

• Electrostatic force of attraction is inversely related to the distance between the opposite charges.

• The smaller the ion, the greater the attraction.

SECTION7.2



• The value of lattice energy is also affected by the charge of the ion.

SECTION7.2


• Relate a formula unit of an ionic compound to its composition.

nonmetal: an element that is generally a gas or a dull, brittle solid and is a poor conductor of heat and electricity

• Write formulas for ionic compounds and oxyanions.

• Apply naming conventions to ionic compounds and oxyanions.

SECTION7.3

Names and Formulas for Ionic Compounds

formula unit

monatomic ion

oxidation number

polyatomic ion

oxyanion

In written names and formulas for ionic compounds, the cation appears first, followed by the anion.

SECTION7.3


Formulas for Ionic Compounds

• When writing names and formulas for ionic compounds, the cation appears first followed by the anion.

• Chemists around the world need to communicate with one another, so a standardized system of naming compounds was developed.

SECTION7.3


Formulas for Ionic Compounds (cont.)

• A formula unit *

• Monatomic ions are *.

SECTION7.3



• Oxidation number, or oxidation state, is *

SECTION7.3


• 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.

• The total charge must equal zero in an ionic compound.


SECTION7.3



• Polyatomic ions are *

• Since polyatomic ions exist as a unit, never change subscripts of the atoms within the ion. If more than one polyatomic ion is needed, place parentheses around the ion and write the appropriate subscript outside the parentheses.

SECTION7.3


SECTION7.3



Names for Ions and Ionic Compounds• An oxyanion is a *.

SECTION7.3


Names for Ions and Ionic Compounds (Cont.)

SECTION7.3


• 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.


SECTION7.3


SECTION7.3



• Describe a metallic bond.

physical property: a characteristic of matter that can be observed or measured without altering the sample’s composition

• Relate the electron sea model to the physical properties of metals.

• Define alloys, and categorize them into two basic types.

SECTION7.4

Metallic Bonds and the Properties of Metals

electron sea model

delocalized electron

metallic bond

alloy

Metals form crystal lattices and can be modeled as cations surrounded by a “sea” of freely moving valence electrons.

SECTION7.4


Metallic Bonds and the Properties of Metals• Metals are not ionic but share several

properties with ionic compounds.

• Metals also form lattices in the solid state, where 8 to 12 other atoms closely surround each metal atom.

SECTION7.4


• Within the crowded lattice, the outer energy levels of metal atoms overlap.

• The electron sea model proposes that all metal atoms in a metallic solid *.

• *and are referred to as delocalized electrons, forming a metallic cation.

SECTION7.4


Metallic Bonds and the Properties of Metals (Cont.)

• A metallic bond is the *

SECTION7.4



• Boiling points are much higher than melting points because of the energy required to separate atoms from the groups of cations and electrons.

SECTION7.4



• Metals are malleable because they can be hammered into sheets.

• Metals are ductile because they can be drawn into wires.

SECTION7.4



• Mobile electrons surrounding positively charged nuclei make metals good conductors of electricity and heat.

• As the number of delocalized electrons increases, so does hardness and strength.

SECTION7.4



Metal Alloys

• An alloy is a *.

–Ex. Stainless steel, brass, cast iron

• The properties of alloys differ from the elements they contain.

–Ex. Steel is iron mixed with at least one other element. Some properties of iron are present, like magnetism, but steel is stronger than iron.

SECTION7.4


Metal Alloys (cont.)

SECTION7.4


• Substitutional alloys are formed when some atoms in the original metallic solid are replaced by other metals of similar atomic structure.

• Interstitial alloys are formed when small holes in a metallic crystal are filled with smaller atoms.

SECTION7.4


Metal Alloys (cont.)

Key Concepts

• A chemical bond is the force that holds two atoms together.

• Some atoms form ions to gain stability. This stable configuration involves a complete outer energy level, usually consisting of eight valence electrons.

• Ions are formed by the loss or gain of valence electrons.

• The number of protons remains unchanged during ion formation.

SECTION7.1

Ion Formation

Study Guide

• Ionic compounds contain ionic bonds formed by the attraction of oppositely charged ions.

• Ions in an ionic compound are arranged in a repeating pattern known as a crystal lattice.

• Ionic compound properties are related to ionic bond strength.

• Ionic compounds are electrolytes; they conduct an electric current in the liquid phase and in aqueous solution.

SECTION7.2


Study Guide

Key Concepts

Key Concepts

• Lattice energy is the energy needed to remove 1 mol of ions from its crystal lattice.

SECTION7.2


Study Guide

Key Concepts

• A formula unit gives the ratio of cations to anions in the ionic compound.

• A monatomic ion is formed from one atom. The charge of a monatomic ion is its oxidation number.

• Roman numerals indicate the oxidation number of cations having multiple possible oxidation states.

• Polyatomic ions consist of more than one atom and act as a single unit.

SECTION7.3


Study Guide

Key Concepts

• To indicate more than one polyatomic ion in a chemical formula, place parentheses around the polyatomic ion and use a subscript.

Study Guide

SECTION7.3


Key Concepts

• A metallic bond forms when metal cations attract freely moving, delocalized valence electrons.

• In the electron sea model, electrons move through the metallic crystal and are not held by any particular atom.

• The electron sea model explains the physical properties of metallic solids.

• Metal alloys are formed when a metal is mixed with one or more other elements.

Study Guide

SECTION7.3


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Chapter 7: Ionic Compounds and Metals. CHEMISTRY Matter and Change