Chapter 7 Honors 2012.ppt

(1)

7.1 Ions

•

_{Chemical Bond}

_{– force that holds two atoms}

together

1.

Positive nucleus to negative electrons

– _Molecules

(2)

7.1 Ions

• _{Chemical Formula – kinds and number of atoms in the}

smallest representative unit of a compound.

1. Molecular Formula – kind and number of atoms in a

molecule.

– _H₂_{O or C}₆_H₁₂_O₆

2. Formula Unit – lowest whole-number ratio of ions in

the ionic compound.

(3)

7.1 Ions

•

_{Ions and Ionic Compounds}

•

_{Ion – atom or group of atoms with a charge.}

• _{Cation – positive charge caused by a loss of}

electrons to become more stable. (Metals) • _{Anion – negative charge caused by a gain of}

electrons to become more stable. (Nonmetals) •

_{Ionic compound – neutral compound}

(4)

7.1 Ions

• _{Monatomic ions – 1 atom ions}

• _{Using the periodic table to find charges}

• _{Noble gases are stable}

• _{Atoms will gain or lose to obtain the}

(5)

Electron Configurations for Cations

•

_{Metals lose electrons to attain noble gas}

configuration.

•

_{They make positive ions. If we look at electron}

configuration it makes sense.

(6)

Ca

2+

Electron Dots for Cations

• _{Metals will have few valence electrons} • _{These will come off}

• _{Forming positive ions}

Ca

40.078

20

(7)

Electron Configurations for Anions

•

_{Nonmetals gain electrons to attain noble gas}

configuration.

•

_{They make negative ions. (anions)}

•

_{Anions ending changes to “-ide”}

•

_{If we look at electron configuration it makes sense.}

•

_{S 1}

_s

2

₂

_s

2

₂

_p

6

_3s

2

₃

_p

4

_{- 6 valence electrons}

•

_S

2-

₁

_s

2

₂

_s

2

₂

_p

6

₃

_s

2

₃

_p

6

_{-noble gas}

(8)

Electron Dots For Anions

• _{Nonmetals will have many valence electrons.} • _{They will gain electrons to fill outer shell.}

(9)

3-•

_{All atoms react to achieve noble gas configuration.}

•

_{Noble gases have two}

_s

_{and six}

_p

_electrons.

•

_{Eight valence electrons .}

•

_{Also called the octet rule.}

(10)

Predicting Ionic Charges

Group 1A

:

_{Lose 1 electron to form}

₁₊

_ions

H

(11)

Predicting Ionic Charges

Group 2A

Group 2A:

:

Loses 2 electrons to form

2+

ions

Be

(12)

Predicting Ionic Charges

Group 3A

:

Loses 3

electrons to form

3+

ions

B

(13)

Predicting Ionic Charges

Group 4A

:

Lose 4

electrons or gain

4 electrons?

Neither!

Group 4A

elements rarely form

(14)

Predicting Ionic Charges

Group 5A

:

Gains 3

electrons to form

3-3-

ions

N

3-

3-P

P

3-

3-As

As

3-

3-Nitride

(15)

Predicting Ionic Charges

Group 6A

:

Gains 2

electrons to form

2-2-

ions

O

2-

2-S

S

2-

2-Se

Se

2-

(16)

Predicting Ionic Charges

Group 7A

:

Gains

1 electron to form

1-1-

ions

F

1-

1-Cl

Cl

1-

1-Br

Br

1-

1-Fluoride

Chloride

Bromide

I

(17)

Predicting Ionic Charges

Group 8A

:

Stable

noble gases

do not

form ions!

(18)

7.1 Forming Chemical Bonds

Element # e

-Nearest

noble

gas

Noble

gas e

-# Gain

or lost

e

-Formula

Mg

12 Ne

10 Lost 2

Mg

2+

Cl

Al

17 Ar

18 Gain 1

Cl

(19)

IONIC BONDING

(20)

Ionic Bonding

Na Cl

transfer of electron

+

(21)

7.2 Ionic Bonds and Ionic Compounds

Ionic compound formation

Al

O

+

O

2-O Al

O

2-O _O

2-Al3+

+

Al3+

(22)

Properties of Ionic Compounds

• _{Crystalline structure.}

• _{A regular repeating arrangement of ions in the solid.} • _{Ions are strongly bonded.}

• _{Structure is rigid.}

• _{High melting points- because of strong forces between}

ions.

(23)

•

_{Conducting electricity is allowing charges to}

move.

•

_{In a solid, the ions are locked in place.}

•

_{Ionic solids are insulators.}

•

_{When melted, the ions can move around.}

•

_{Melted ionic compounds conduct.}

•

_{First get them to 800ºC.}

(24)

Do they conduct?

•If a voltage is applied across this molten mass, cations migrate freely to one electrode and anions migrate to the other.

(25)

(26)

Ionic solids are brittle

+

-

+

-+

-

+

-

+

-+

-

+

Force

+

-

+

(27)

7.2 Ionic Bonds and Ionic Compounds

Properties of ionic compounds

•

_{Crystalline solids with high melting points}

•

_Brittle

•

_{Usually metal and nonmetal in compound}

•

_{Highly water soluble}

•

_{Nonconductor as a solid}

•

_{Conductor when a molten or aqueous}

(28)

7.2 Ionic Bonds and Ionic Compounds

• _{Lattice Energy – energy needed to}

separate electrons (1 mole) from the ionic

compound

•

_{Smaller atoms have higher lattice energies}

• _{More shells and shielding make lower lattice}

energies

•

_{Greater charged ions have higher lattice}

(29)

The

coordination number

of an ion is the

number of ions of opposite charge that

surround the ion in a crystal.

• In NaCl, each ion has a

coordination number of 6.

– The coordination number of Na+ is 6 because each Na+ ion

is surrounded by six Cl– ions.

– The coordination number of Cl–

is also 6 because each Cl– ion

(30)

Properties of Ionic Compounds

In CsCl, each ion has a coordination

number of 8.

• Each Cs

+

ion is

surrounded by

eight Cl

–

ions.

• Each Cl

–

ion is

(31)

7.2 Ionic Bonds and Ionic Compounds

The formula of an ionic compound

is the fewest cations and anions

(32)

Writing Formulas of Ionic Compounds

•

_{Chemical Formula has a neutral charge:}

it shows types of atoms and how many of each

To write an ionic compound’s formula, we need:

(33)

No overall charge!

• _Na1+ and F

1-• _Ba2+ and O

2-• _Na1+ and O

2-• _Ba2+ and F

1-NaF

BaO

Na

2

O

(34)

InBr₃ BaS

Criss-Cross Rule

Charge on cation “becomes” subscript of anion Charge of anion “becomes” subscript of cation

**Warning: Reduce to lowest terms

Al₂O₃ Al3+_{and O}2–

Al₂ O₃

Ba2+_{and S}2–

Ba₂ S₂

In3+_{and Br}1–

In₁ Br₃

(35)

• _{1. Name the cation first, then anion}

• _{2. Monatomic cation = name of the}

element

Ca

2+

= calcium

ion

• _{3. Monatomic anion =}

_root

₊

_-ide

Cl



_{= chlor}

_ide

(36)

Naming Binary Compounds

Formula Name

1 BaO ____________________

2 ________________ sodium bromide

3 MgI₂ ____________________

4 KCl ____________________

5 ________________ strontium fluoride

6 ________________ cesium fluoride

barium oxide

NaBr

magnesium iodide

potassium chloride

SrF₂

(37)

• _{Groups of atoms that stay together and have an}

overall charge, and one name. •

_{Usually end in –ate or -ite}

•

Acetate:

C

₂

H

₃

O

₂

1-•

Nitrate:

NO

₃ 1-•

Nitrite:

NO

₂

1-•

Permanganate:

MnO

₄

(38)

1-Rules for Parentheses

Parentheses are used only when the following two condition are met:

1. There is a polyatomic ion present and…

2. There are two or more of that polyatomic ion in the formula.

Examples:

NaNO₃ NO₃1- is a radical, but there is only one of it.

Co(NO₃)₂ NO₃1- is a radical and there are two of them

(NH₄)₂SO₄ NH₄1+_{is a radical and there are two of them;}

SO₄2-_{is a radical but there is only one of it.}

NaOH OH1-_{is a radical but there is only one of it.}

Co(OH)₂ OH1-_{is a radical and there are two of it.}

Al₂(CO₃)₃ CO₃2- is a radical and there are three of them.

(39)

Formulas with Polyatomic Ions

Ba

2+

NO

3

3 -

-Example: Barium nitrate

1. Write the formulas for the cation and anion, including CHARGES!

2. Check to see if charges are balanced.

3. Balance charges , if necessary,

using subscripts. Use parentheses if you need more than one of a

polyatomic ion. Use the criss-cross

method to balance subscripts.

Not balanced!

( )

₂

Now balanced.

(40)

Writing Ionic Compound

Formulas

Example: Ammonium sulfate 1. Write the formulas for the cation and anion, including

CHARGES!

NH

4

4 +

+

SO

4

4 2-

2-2. Check to see if charges are balanced.

method to balance the subscripts.

Not balanced!

( )

2

Now balanced.

(41)

Writing Ionic Compound

Formulas

Example: Aluminum phosphate 1. Write the formulas for the

cation and anion, including

CHARGES!

Al

3+

PO

4

4 3-

3-2. Check to see if charges are

balanced. They ARE balanced!

(42)

Writing Ionic Compound

Formulas

Example: Magnesium carbonate 1. Write the formulas for the

cation and anion, including

CHARGES!

Mg

2+

CO

3

3 2-

2-2. Check to see if charges

are balanced. They are balanced!

(43)

Writing Ionic Compound

Formulas

Example: Aluminum sulfide 1. Write the formulas for the cation and anion, including

CHARGES!

Al

3+

S

2-

2-2. Check to see if charges are balanced.

using subscripts. Use parentheses if

you need more than one of a

Not balanced!

2

3 ₃

Now balanced.

(44)

Writing Ionic Compound

Formulas

Example: Zinc hydroxide

1. Write the formulas for the cation and anion, including

CHARGES!

Zn

2+

OH

-

-2. Check to see if charges are balanced.

Not balanced!

( )

₂

Now balanced.

(45)

Writing Ionic Compound

Formulas

Example: Iron (III) chloride 1. Write the formulas for the cation and anion, including

CHARGES!

Fe

3+

Cl

-

-2. Check to see if charges are balanced.

Not balanced!

3

Now balanced.

(46)

Naming Ionic Compounds

• _{some metals can form more than one}

charge (usually the transition metals)

•

_{use a}

_{Roman numeral}

_{in their name:}

PbCl

₂

– use the

anion

to find the charge on the

cation (chloride is always 1-)

Pb

2+

is the lead (II) cation

PbCl

₂

= lead (

II

) chloride

(47)

Things to look for

• _{If cations have (_), the number in}

parenthesis is their charge.

• _{If anions end in}

_-ide

_{they are}

probably off the periodic table

(Monoatomic)

• _{If anion ends in}

_-ate

_or

_–ite

_,

_then

(48)

Names and Formulas for

IonicCompounds

• _{Transition Metal Ions}

• _{Many transition metals can be stable at several charges.}

• _Fe2+_{, Fe}3+_{, Cu}+_{, Cu}2+_{, Hg}

2+2, Hg+2, Sn2+, Sn4+, Pb2+, and Pb4+!

• _{Use Roman numerals and parenthesis to distinguish between}

different ions.

Fe

2+

Fe

3+

iron (II)

iron (III)

(49)

Predicting Ionic Charges

Group B elements

:

_Many

_transition

_elements

have

more than one

possible oxidation state.

Iron (II) = Fe

2+

Iron (III) = Fe

3+

Note the use of

Roman

(50)

Predicting Ionic Charges

Some of the

post-transition

elements also

have

more than one

possible oxidation state.

Tin (II) = Sn

2+

_{Lead (II) = Pb}

₂₊

(51)

Predicting Ionic Charges

Group B elements

:

_Some

_transition

_elements

have

only one

possible oxidation state, such

as these three that are always:

Zinc = Zn

2+

(52)

Exceptions:

• _{Some of the transition metals}

have only one ionic charge:

• _{Do not use roman numerals for}

these:

• _Silver

_{is always 1+ (}

_Ag

1+

)

• _Cadmium

_and

_Zinc

_{are always}

(53)

Criss-Cross Reduce

1. Criss-cross the charge values as subscripts 2. Reduce if you can

Fe

3+

SO

4

2-2 3

2 and 3 can’t be reduced!

Fe

₂

(SO

₄

)

₃

iron(III) sulfate tin(IV) oxide

Sn

4+

O

2-2 4

2 and 4 can be reduced to 1 and 2

1 2

(54)

Names and Formulas for Ionic

Compounds

Naming Ionic Compounds

1. Name the cation 1st and anion 2nd.

2. Copy the names of the ions from the back of the periodic

table.

• _{Monatomic cations use the element name.}

• _{Monatomic anions use the root of the element name}

plus the suffix -ide.

• _{If an element can have more than one charge state,}

use a Roman numeral in parentheses after the

(55)

Compounds

• _{What is the name for MgO?}

Mg2+ and O

magnesium oxide

• What is the name of CuSO₄?

Cu+ or Cu2+ and (SO 4)

2-copper (II) sulfate

Use your anion

(56)

7.3 Bonding in Metals

• _{How atoms are held together in the solid.}

• _{Metals hold onto their valence electrons very weakly.} • _{Think of them as positive ions floating in a “sea of}

electrons”.

• _{Electrons that are free to move in metals are called}

(57)

Metallic Bonds

Metallic bond- force of attraction between free floating valence electrons and positively charged metal ions. (electron sea)

Properties of metals

• _{Usually solids}

• _{Usually high melting point}

(58)

Sea of Electrons

• _{Electrons are free to move through the solid.} • _{Metals conduct electricity.}

+ + + +

(59)

• _{Hammered into shape (bend).} • _{Ductile - drawn into wires.}

• _{Electrons allow atoms to slide by.}

(60)

Metallic Substances

Alloy - mixture of two or more elements (1 must be a metal). Types of alloys

• _{Substitutional – atoms of metal are replaced by atoms of similar size}

• _{Sterling silver, brass, 10-carat gold}

• _{Interstatial – small atoms put in between metal atoms}