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Ionic Compounds and Metals Chemistry Unit 6

Chem unit 6 presentation

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Page 1: Chem unit 6 presentation

Ionic Compounds and

MetalsChemistry Unit 6

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

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

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

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

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Ion FormationIons are formed when atoms gain

or lose valence electrons to achieve a stable octet electron configuration.

Goals and Objectives:

Define a chemical bond.

Describe the formation of positive and negative ions.

Relate ion formation to electron configuration.

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Valence Electrons and Chemical

BondsChemical Bond – is a force that holds two atoms together.

They can form between the positive nucleus of one atom and the negative valence electrons of another atom or between two oppositely charged ions.

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Valence Electrons and Chemical

BondsAtom’s try to form the octet – the stable arrangement of eight valence electrons in the outer energy level – by gaining or losing valence electrons.

The transfer of valence electrons between two atoms is based on the ionization energy and electron affinity of the two atoms.

Noble gases- high ionization energy + low electron affinity = little chemical reactivity.

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Positive Ion Formation

Cation – positively charged ionExample:

Sodium atom:1s2 2s2p6 3s1

Sodium ion:1s2 2s2 p6 = neon

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Positive Ion Formation

Metal atoms are reactive because they lose valence electrons easily.

Group 1: commonly form +1 ionsGroup 2: commonly form +2 ionsGroup 13: sometimes +3 ions

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Positive Ion Formation

Transition metal ions have an outer shell of s2

They will lose their s electrons and occasionally a d electron.Typically form +2 or +3 ions but can form greater than +3 ions

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Positive Ion Formation

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

Groups 11-14 will lose electrons to form full outer shells: s, p, and d.

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Negative Ion Formation

An anion is a negatively charged ion. (Add “-ide” to the end of the root atom name.)

Nonmetals easily gain electrons.Example:

Chlorine atom:1s2 2s2p6 3s2p5

Chlorine ion:1s2 2s2p6 3s2p6 = Argon

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Negative Ion Formation

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

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

Phosphorus can gain 3 or lose 5Group 15 usually gains 3 electronsGroup 16 usually gains 2 electronsGroup 17 usually gains 1 electron

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Practice Problems

CALM 6:1

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Ionic Bonds and Ionic Compounds

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Ionic Bonds and Ionic Compounds

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

Goals and Objectives:

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

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

Categorize ionic bond formation as exothermic or endothermic.

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Ionic Bond

Ionic Bond is the electrostatic force that holds oppositely charged particles together.

Ionic Compound is a compound that contains an ionic bond.

Ionic bonds between metals and oxygen are called oxides.Most other ionic compounds are considered salts.

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Binary Ionic Compound

Binary Ionic compound is an ionic compound that contains two different elements.

One metallic cation and a nonmetallic anion.Examples: NaCl, MgO, KBr, LiF

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Ionic Bond Formation

Electrons gained and lost in each element must be equal. (conservation of electrons)

Calcium and Fluorine

Aluminum and Oxygen

Sodium and Chlorine

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Properties of Ionic Compounds

Compounds are organized such that a pattern repeats to balance attraction and repulsion

Total charge of a compound is neutral

Often highly organized

Example: NaCl crystal

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Crystal Lattice

A crystal lattice is a three dimensional geometric arrangement of particles.

Each negative ion is surrounded by a positive ion which results in strong attractions between ions.Size and shape are dependent on relative numbers of ions.

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Crystal LatticePhysical Properties:

Characteristics of bond strength – ionic bonds are relatively strong and take a large amount of energy to break.

Melting point – highBoiling point – highHardness of material is high: rigid and brittle solids.

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Properties of Ionic Compounds

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Crystal LatticeCharacteristics of the compound:

Conducts electricity, conditionallyIons in solid state ionic compounds are locked in place and they do not have free electrons in order to conduct electricity.Ionic compounds that are melted or dissolved in aqueous solutions have ions that are free to move and therefore do conduct electricity

Electrolyte – an ionic compound that conducts electricity in an aqueous solution.

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Energy and the Ionic Bond

Formation of ionic compounds forms a more stable system and therefore reduces the energy required to sustain it.

Since the creating of bonds lowers energy, energy is released in the process. The creation of bonds is said to be Exothermic.

Exothermic – energy is released during a chemical reaction.

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Energy and the Ionic Bond

Breaking of ionic compounds reduces the stability of a system and therefore increases the energy required to sustain it .

Since the creating of bonds lowers energy, the breaking of bonds increases energy and therefore it is required for the process.

Endothermic – energy is absorbed during a chemical reaction.

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Lattice EnergyLattice energy is the energy required to separate 1 mole of the ions of an ionic compound.

higher the lattice energy the stronger the bond strength.Directly related to the size of the ions bonded.

smaller ions form compounds more closely because attraction increases with decreased distance.

Also affected by charge of ionsHigher ion charge typically has higher lattice energy.

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Lattice Energy

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Practice ProblemsCALM 6:2

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Names and Formulas for Ionic

Compounds

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Names and Formulas for Ionic

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

Goals and Objectives:

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

Write formulas for ionic compounds and oxyanions.

Apply naming conventions to ionic compounds and oxyanions.

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Formulas for Ionic Compounds

A standardized system for naming compounds was developed for much the same reason as the SI unit system. This serves as a universal naming system for communication among the science community.

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Formula UnitA formula unit is the chemical formula for an ionic compound and represents the simplest ratio of ions.

MgCl2 not Mg4Cl8

A monoatomic ion is a one atom ion.

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Oxidation number

Oxidation number (oxidation state) the charge of a monatomic ion.

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Formulas for Ionic Compounds

The symbol for the cation is written first with the anion second.

Subscripts represent the number of atoms of each element in a compound.

The total charge must equal zero in an ionic compound.

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Polyatomic IonsPolyatomic ions are made up of more than one atom.

Formulas for polyatomic ionic compounds

Charge applies to the entire group of atoms.Parentheses are used if more than one polyatomic ion is needed to balance a compound.

Do not change subscripts within the ion groupExample (NH4)O

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Polyatomic Ions

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Oxyanion

An oxyanion is a polyatomic negative ion composed of an element, usually a nonmetal, bonded to one or more oxygen.

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Oxyanion Naming Rules

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Names for Ions and Ionic

Compounds1. Name the cation followed by the

anion.

2. For monatomic cations, use the element name.

3. For monatomic anions, use the root of the element with the suffix –ide.

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Names for Ions and Ionic

Compounds4. Multiple oxidation states are represented by a Roman numeral in paranthesis after the cation.a) This applies to transition metals with

more than one oxidation state and not the Group 1 and 2 cations.

b) Example: FeO is Iron (II) oxide; Fe2O3 Iron (III) oxide.

5. With a polyatomic ion, name the cation followed by the name of the polyatomic ion.a) Example: NaOH is sodium

hydroxide.

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Problem Solving

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Practice Problems

CALM 6:3

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Metallic Bonds and the

Properties of Metals

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Metallic Bonds and the

Properties of MetalsMetals form crystal lattices and can be

modeled as cations surrounded by a “sea” of freely moving valence electrons.

Goals and Objectives:

Describe a metallic bond.

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

Define alloys, and categorize them into two basic types.

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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.

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

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Electron Sea Model

The electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electron.

The electrons are free to move around and are referred to as delocalized electrons, forming a metallic cation.

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Metallic Bonds

A metallic bond is the attraction of an metallic cation for delocalized electrons

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Properties of Metals

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

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Properties of Metals

Metals are malleable because they can be hammered into sheets.

Metals are ductile because they can be drawn into wires.

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Properties of Metals

Mobile electrons around cations make metals good conductors of electricity and heat.

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

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Metal Alloys

An alloy is a mixture of elements that has metallic properties.

The properties of alloys differ from the elements they contain.

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Metal Alloys

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Metal Alloys

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.

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Practice Problems

CALM 6:4

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Accumulating Content

How does the electron configuration of a neutral element compare to that of its ion configuration?

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Accumulating Content

How does energy and stability relate to ion formation and bond formation?

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Accumulating Content

What are some physical and chemical properties of metals that are caused by the way they ionize or bond?

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Study GuideKey Concepts

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Key ConceptsA 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.

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Key Concepts

The number of protons remains unchanged during ion formation.

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

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Key Concepts

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.

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

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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.

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Key Concepts

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

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

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

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Key Concepts

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.

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QuestionsCations form when atoms _______

electrons.

A.gain

B. lose

C. charge

D.delocalize

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QuestionsWhat is the repeating pattern of atoms in

an ionic solid called?

A.crystal lattice

B. ionic lattice

C. energy lattice

D.ionic bonding

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QuestionsGive the name of the following: NaClO4

A.sodium hypochlorite

B. sodium chlorite

C. sodium chlorate

D.sodium perchlorate

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QuestionsAs the distance between ions in an ionic

bond is shortened,

A. the energy to break the bond decreases.

B. the electrostatic attraction decreases.

C. the electrostatic attraction increases.

D.the ionic bond changes to a metallic bond.

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QuestionsAn alloy is what type of substance?

A.heterogeneous mixture

B. compound

C. mixture of elements

D.element

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QuestionsWhich is NOT true about metallic solids?

A.Metals are shiny.

B. Metals are good conductors of heat and electricity.

C. Metals are ductile.

D.Metals have relatively low boiling points.

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QuestionsElectrons in an atom’s outer most energy

level are referred to as what?

A. ions

B. cations

C. valence electrons

D.noble-gas electrons

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QuestionsWhat is the oxidation state of copper in

Cu(II)Cl2?

A.1+

B. 2+

C. 2–

D.unable to determine

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QuestionsWhich elements naturally occur with a full

octet of valence electrons?

A.alkali metals

B. alkali earth metals

C. halogens

D.noble gases

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QuestionsHow many electrons are in a full octet?

A.10

B. 8

C. 6

D.4

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The End