IonicCompounds and Metals

Chapter 7

Vocabulary Ch. 7.1

Chemical bond Cation Anion

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Ch. 7.2 Ionic bond Ionic compound Binary

compound Crystal lattice Electrolyte Lattice energy

Objectives Define a chemical bond Describe how ions form Identify ionic bonding and the

characteristics of ionic compounds Name and write formulas for

binary compounds Polyatomic ion containing compounds Compound with metals that have multip

le oxidation states Hydrates

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Forming Compounds The Octet Rule: Atoms become stable

by having 8 electrons in their outer energy level (2 for smaller atoms) Similar arrangement of valence

electrons for element in the same group. (Ex: ns1 for alkali metals)

Electron arrangements determines chemical properties

Presents a model of chemical stability When they have gotten 8 electrons they

have achieved NOBLE GAS CONFIGURATION

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Forming Compounds

atoms collide with enough energy

outer electrons move to achieve a stable octet of valence electrons (noble gas configuration).

atoms formed a new compound Total # of e- must remain the

same. Electrons are particles of matter.

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Forming Compounds Transfer of Electrons

.. ..Na· + ·Cl: [Na]+ + [:Cl:]-

˙˙ ˙˙

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Lattice Energy

Ionic compounds consist of a crystal lattice of positive and negative ions, which is a repeating pattern of ions.

= Cl-

= Na+

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Lattice Energy

The lattice energy is the energy required to separate the ions from their crystalline solid state.

Increases with decreasing ionic size.

Increases with increasing ionic charge.

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Lattice energy decreases as anion gets bigger!!

Lattice energy is large due to +2 and -2 Charges; decreases as ions get larger.

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Lattice EnergyPhysical Properties of ionic compounds: The melting point increases as

lattice energy increases. Solutions are electrolytes, which

conduct an electric current. Force applied to crystals causes them

to shatter.

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Vocabulary Ch. 7.3

Formula UnitMonoatomic ionOxidation NumberPolyatomic ion

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Names and Formulas

Rules for naming binary compounds

1. Name the cation first. This is usually a metal. Use element name.

2. Then name the anion using the 1st syllable of the of the element name and then end in –ide.

Example: Potassium Chloride (KCl)

Magnesium Oxide (MgO)

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Binary Compound Naming PracticeFormula NaF Al2S3

CaO Mg3N2

CaH2

Name

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Predicting Charge on Ions

Can you predict the charge on an ion depending on where it is in the periodic table?

Yes, of course. Group numbers can help predict many charges. For groups 1 & 2 – they lose electrons

and become positive Group 13 – loses 3 electrons and are

generally positive Groups 15 – 17 gain electrons and

become negative in ions.17

Predicting Charge on Ions

The charge on a monoatomic ion is the

Oxidation number

Again, oxidation number for many elements in the main group (Groups 1 & 2, 13-18) can be predicted by looking at the group number.

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Rules For Writing Ionic Compound Formulas

1. Write cation symbol first. (Same as we did in naming them.)

2. Write anion symbol second.3. Add subscripts such that the sum of

the charges is zero.4. Write the simplest ratio of ions.

This is the formula unit.

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Writing Ionic Formula

Example: What is the formula for Aluminum Oxide? What is charge on aluminum when it is

an ion? What is charge on oxygen when it is an

ion (oxide)? How do we get the charges to balance?

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Use it backward—knowing compoundFigure out charges

Method of “Cross-Multiplying”

What would be the subscriptsto make the Sum = 0?

Drop the signs and make the numbers subscripts

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Examples of Writing Formulas

(Binary Compounds)Name of Compound Lithium oxide

Lithium ions and oxide ions Li+ O2-

Calcium chloride Calcium ions and chloride ions

Ca2+ Cl-

Magnesium nitridemagnesium ions and nitride ions

Mg2+ N3-

Formula of Compound

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Practice Writing Binary Compound FormulasName of

Compound Lithium iodide Beryllium

chloride Calcium oxide Sodium oxide Strontium

sulfide Calcium

phosphide

Formula of Compound

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Compounds of Metals with Multiple Oxidation States

(Multivalent Metals) Includes metals in Groups 3 through

12 of the periodic table And the representative metals in

Groups 13 & 14 (Commonly Sn & Pb, but also Ga, In, and Tl)

They have more than one

Oxidation State So they can form more than one

type of positive ion.24

Compounds of Multivalent Metals

For Example:Copper can exist as Cu+ and

Cu2+

Iron can exist as Fe2+ and Fe3+

Exceptions: Zn and Ag. Zinc only forms a Zn2+ ion Ag only forms a Ag+ ion

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Compounds of Multivalent Metals

How do chemists distinguish the names of compounds formed these metals?

We use Roman numerals in parenthesis after the name of the element.

Copper Ion

Chloride Ion

Formula Name

Cu+ Cl- CuCl Copper (I) Chloride

Cu2+ 2Cl- CuCl2 Copper (II)

Chloride26

Compounds of Multivalent Metals

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Compounds of Multivalent Metals

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Formulas of Multivalent Metals

How to write a formula containing one of these metals. First, look at the name.

Example: if it is Manganese (III) it means that it’s Mn3+

The roman numeral is the oxidation number of the ion, not how many there are!!!!

Then, you can balance charges as before.

Example: MnCl3

Manganese is 3+ and chloride is always 1-.

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Writing Names of Multivalent Metal

Compounds If your given a formula, how do you

figure out the name? Determine the charge on the metal

ion. Look at the negative ion. Figure out what was needed to make

the compound neutral Example: FeCl3

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Compounds of Multivalent Metals

Given name or formula Iron(II) oxide

MnF3

Nickel(II) chloride

PbS2

Determine formula or name

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What is the oxidation number of Zinc when it’s an ion?

a) 1+ or 2+

b) 2+ always

c) 1+ always

d) 1- or 2-

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What is the formula for iron(II) oxide?

a) Fe2O

b) FeO2

c) Fe2O2

d) FeO

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What is the correct name of MnF3?

a) Manganese (I) fluorideb) Magnesium (I) fluoridec) Manganese (III) fluorided) Magnesium (III) fluoride

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What is the correct formula for nickel(II) chloride?

a) Ni2Cl

b) NiC2

c) NiCl2d) Ni2Cl2

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What is the name of PbS2?

a) Lead (IV) sulfide

b) Lead (I) sulfide

c) Lead (II) sulfide

d) Lead (III) sulfide

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Polyatomic Ions

Ions can contain more than one element.

An ion with two or more different elements is a

Polyatomic Ion In polyatomic ions, the atoms are

covalently bonded and the atoms share electrons.

Individual atoms have no charge, but the group has an overall charge.

Example: SO42- (Sulfate)

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Common Polyatomic IonsName of Ion Formula Charg

eAmmonium NH4

+ 1+

Hydrogen carbonate

(bicarbonate)

HCO3- 1-

Hydrogen sulfate

HSO4- 1-

Acetate C2H3O2- 1-

Nitrite NO2- 1-

Nitrate NO3- 1-

Cyanide CN- 1-Hydroxide OH- 1-

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Common Polyatomic Ions

Name of Ion Formula Charge

Dihydrogen phosphate

H2PO4- 1-

Permanganate MnO4- 1-

Carbonate CO32- 2-

Sulfate SO42- 2-

Sulfite SO32- 2-

Oxalate C2O42- 2-

Monohydrogen phosphate

HPO42- 2-

Dichromate Cr2O72- 2-

Phosphate PO43- 3-

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Compounds Containing Polyatomic Ions

1. When there is more than one polyatomic ion, treat it as if it were a single ion by keeping it together as a unit using parenthesis.

2. Write a subscript outside the parenthesis to show how many units there are of polyatomic ion.

3. Remember that the sum of the charges must equal zero.

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Examples of Writing Formulas

(w/Polyatomic Ions)Name of Compound Calcium nitrate

Calcium ions and nitrate ions Ca2+ NO3

1-

Sodium carbonateSodium ions and carbonate ions

Na+ CO32-

Lead(II) Phosphate lead 2+ ions and phosphate ions

Pb2+ PO43-

Formula of Compound

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Naming Polyatomic Compounds

from formulas1. Positive ion (usually a metal) is

named first as before.2. Negative polyatomic ion name

as listed in the chart is second. Note: If you see more than one

element after the metal the rest is a polyatomic ion. Look for that group in the chart.

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Polyatomic Ion Practice

Given name or formula: NaHCO3

Lithium Acetate Ca(CN)2

Copper(II) Hydroxide K2Cr2O7

Fe(HCO3)3

Ammonium Chloride

Determine formula or name

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What is the formula for zinc arsenate?

Note: You have to type this in. Hit the ‘Shift’ key (lower right) to

get capital letters. If you need parenthesis, hit sym 4

for ‘(‘ and sym 5 for ‘)’.

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Ch. 7.4 Vocabulary

Ch. 10.5 Hydrate (page

351)

Ch. 7.4 Electron Sea

model Delocalized

electron Metallic Bond Alloy Interstitial alloy Substitutional

Alloy46

Compounds of Hydrates (Ch. 10.5)

Hydrate – when there is a specific amount of water in the crystal of a compound.

The water molecules are part of the crystal structure of the ionic compound.

Many compounds become hydrates by absorbing water from the air. The water then becomes part of its structure.

Many of them are used as drying agents (desiccants).

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Compounds of Hydrates

When writing a formula for a hydrated compound use a dot (•) followed by the number of water molecules.

Example: CaCl2•2H2O

This means that this hydrated chloride compound has 2 molecules of water for each formula unit of calcium chloride. 48

CaCl2•2H2O

Ca+2 Cl-Cl- Cl-

Water

Water

-

-

Compounds of Hydrates

CaCl2•2H2O This means that this hydrated chloride

compound has 2 molecules of water for each formula unit of calcium chloride.

You would call the compound Calcium chloride dihydrate.

Rule: Follow the regular name of the compound with the word “hydrate.” The prefix before “hydrate” tells you how many water molecules there are.

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Prefixes for HydratesMolecules of Water Prefix

1 Mono-2 Di-3 Tri-4 Tetra-5 Penta-6 Hexa-7 Hepta-8 Octa-9 Nona-10 Deca- 51

Hydrate Compound Practice

Given Name or Formula

MgSO3•6H2O

Strontium oxalate monohydrate

Ni3(PO4)2•7H2O

Lead(II) acetate trihydrate

Determine the Formula or Name

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Compounds of Hydrates

Hydrates can also lose water molecules, usually by heating.

They may even have a different color than the hydrated compound.

When they lose their water molecules, they become anhydrous (without water). 53

Ch. 7.4 - Metal Bonding – Electron Sea Model

There are not enough electrons for the metal atoms to be covalently bonded to each other.

We use a delocalized model for electrons in a metal

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Delocalized Electrons in a Metal

The metal nuclei are seen to exist in a sea of electrons.

No electrons are localized between any two metal atoms.

Therefore, the electrons can flow freely through the metal.

Without any definite bonds, the metals are easy to deform (and are malleable and ductile).

The more delocalized e-, the harder and stronger the metal.

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Delocalized Model for Electrons in a Metal

Melting Point

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Malleability

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Metals, above, compared to ionic compounds, below.

Alloys Alloys are homogeneous mixtures,

metal solutions, really. Substitutional alloys:

atoms must have similar atomic size, elements must have similar bonding

characteristics. Interstitial alloys:

one element much smaller than the other in order to fit into the interstitial sites, e.g. a nonmetal.

The alloy is much stronger than the pure metal (increased bonding between nonmetal and metal).

Example steel (contains up to 3% carbon).

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Alloys

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Common Alloys

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