Chapter 7 “Ionic and Metallic Bonding” Chemistry January 14, 2011

Chapter 7

“Ionic and Metallic Bonding”

Chemistry

January 14, 2011

Bellringer #55 (Jan 14th, 2011) Based on what you read for your

homework:

– What is the rule that atoms tend to follow when forming ions?

– How can you determine the number of valence electrons in an atom of a representative element?

Agenda (Jan 14th, 2011) Answer Bellringer #55 Check Cornell notes 7.1 Write OBJECTIVES for section 7.1 Notes/Lecture 7.1 Answer “Pair to Pair” questions Hmwk: Section 7.1 assessment and 7.1

Wkst

Section 7.1 - Ions

OBJECTIVES:

–Determine the number of valence electrons in an atom of a representative element.

Section 7.1 - Ions

OBJECTIVES:

–Explain how the octet rule applies to atoms of metallic and nonmetallic elements.

Section 7.1 - Ions

OBJECTIVES:

–Describe how cations form.

Section 7.1 - Ions

OBJECTIVES:

–Explain how anions form.

Valence Electrons are…? The electrons responsible for the

chemical properties of atoms, and are those in the outer energy level.

Valence electrons - The s and p electrons in the outer energy level

–the highest occupied energy level Core electrons – are those in the

energy levels below.

Keeping Track of Electrons Atoms in the same column...

1) Have the same outer electron configuration.

2) Have the same valence electrons. The number of valence electrons are

easily determined. It is the group number for a representative element

Group 2A: Be, Mg, Ca, etc.

– have 2 valence electrons

Pair to Pair Question #1 Determine how many valence electrons are in

the following atoms:– Rubidium (Rb)– Barium (Ba)– Aluminum (Al)– Fluorine (F)– Argon (Ar)– Helium (He)– Nitrogen (N)– Sulfur (S)

Electron Dot diagrams are… A way of showing & keeping

track of valence electrons. How to write them? Write the symbol - it

represents the nucleus and inner (core) electrons

Put one dot for each valence electron (8 maximum)

They don’t pair up until they have to…..what rule does this sound like?

Hund’s Rule

X

The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons to show.

First we write the symbol. NThen add 1 electron at a time to each side.Now they are forced to pair up.

We have now written the electron dot diagram for Nitrogen.

The Octet Rule In Chapter 6, we learned that noble gases

are unreactive in chemical reactions The Octet Rule: in forming compounds,

atoms tend to achieve a noble gas configuration; 8 in the outer level is stable

Each noble gas has 8 electrons, except for one…..which one is it???????

Helium is an exception in Group 8A because it only has 2 electrons

Pair to Pair Question #2 Draw the ELECTRON DOT DIAGRAM for the

following atoms:– Aluminum– Silicon– Nitrogen– Sulfur– Fluorine– Argon– Barium– Rubidium

Formation of Cations Metals lose electrons to attain a noble

gas configuration. They make positive ions (cations) If we look at the electron configuration,

it makes sense to lose electrons: Na 1s22s22p63s1 1 valence electron Na1+ 1s22s22p6 This is a noble gas

configuration with 8 electrons in the outer level.

Electron Dots For Cations Metals will have few valence electrons

(usually 3 or less); calcium has only 2 valence electrons

Ca

Electron Dots For Cations Metals will have few valence electrons Metals will lose the valence electrons

Ca

Electron Dots For Cations Metals will have few valence electrons Metals will lose the valence electrons Forming positive ions

Ca2+NO DOTS are now shown for the cation.

This is named the “calcium ion”.

Electron Dots For CationsLet’s do Beryllium, #4The electron configuration is:

1s22s2

Thus, it can lose 2e- (making it 2+), to be like Helium

Be = Be2+ Beryllium ion

Pair to Pair Question #3 Draw the ELECTRON DOT

STRUCTURES for the following CATIONS:

– Calcium (Ca)

– Sodium (Na)

– Gallium (Ga)

Electron Configurations: Anions Nonmetals gain electrons to attain

noble gas configuration. They make negative ions (anions) S = 1s22s22p63s23p4 = 6 valence

electrons S2- = 1s22s22p63s23p6 = noble gas

configuration. Halide ions are ions from chlorine or

other halogens that gain electrons

Electron Dots For Anions Nonmetals will have many valence

electrons (usually 5 or more) They will gain electrons to fill outer shell.

P 3-(This is called the “phosphide ion”, and should show dots)

Electron Dots For AnionsLet’s do Chlorine, #17The electron configuration is:

1s22s22p63s23p5

Thus, it can gain 1e- (making it 1-), to be like Argon

Cl = Cl 1-

Chloride ion

Pair to Pair Question #4 Draw ELECTRON DOT STRUCTURES

for the following ANIONS:

– Phosphorous (P)

– Bromine (Br)

– Sulfur (S)

Stable Electron Configurations All atoms react to try and achieve a

noble gas configuration. Noble gases have 2 s and 6 p electrons. 8 valence electrons = already stable! This is the octet rule (8 in the outer level

is particularly stable).

Ar

Bellringer #56 (Jan 18th, 2011) Write the ELECTRON DOT DIAGRAMS

of the NEUTRAL atom AND ION for the following elements:

– Bromine

– Boron

– Strontium

****each element should have TWO electron dot diagrams

Agenda Objective: Review for Semester Exam Bellringer #56 Homework Check Results of Semester Exam: 1st attempt Semester Exam Study Guide Science Fair Make-Up Update Homework: Cornell Notes 7.2 Semester Exam 2nd Attempt: Tomorrow

Bellringer #57 (Jan 20th, 2011) According to Section 7.2

– What is an IONIC COMPOUND?

– What are three properties of ionic compounds?

Agenda (Jan 20th, 2011) Bellringer #57 Homework Check: 7.2 Cornell Notes Write Section 7.2 Objectives 7.2 Notes/Lecture Peer-to-Peer Questions (turn in at end

of class) Homework: 7.2 Section Assessment

(#14-22)

Section 7.2 Ionic Bonds and Ionic Compounds

OBJECTIVES:

–Explain the electrical charge of an ionic compound.

Section 7.2 Ionic Bonds and Ionic Compounds

OBJECTIVES:

–Describe three properties of ionic compounds.

Ionic Compounds

1) Also called SALTS

2) Made from: a CATION with an ANION (or literally from a metal combining with a nonmetal)

Ionic Bonding Anions and cations are held together

by opposite charges (+ and -) Ionic compounds are called salts. Simplest ratio of elements in an ionic

compound is called the formula unit. The bond is formed through the

transfer of electrons (lose and gain) Electrons are transferred to achieve

noble gas configuration.

Ionic Bonding Example

Na ClThe metal (sodium) tends to lose its one electron from the outer level.

The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.

Ionic Bonding Example

Na+ Cl -

Note: Remember that NO DOTS are now shown for the cation!

Ionic Bonding Example

All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable).

Ca P

Lets do an example by combining calcium and phosphorus:

Ionic Bonding

Ca P

Ionic Bonding

Ca2+ P

Ionic Bonding

Ca2+ P

Ca

Ionic Bonding

Ca2+ P 3-

Ca

Ionic Bonding

Ca2+ P 3-

Ca P

Ionic Bonding

Ca2+ P 3-

Ca2+ P

Ionic Bonding

Ca2+ P 3-

Ca2+ P

Ca

Ionic Bonding

Ca2+ P 3-

Ca2+ P

Ca

Ionic Bonding

Ca2+ P 3-

Ca2+P

3-

Ca2+

Ionic Bonding

P3-Ca2+

Ca3P2

If you want to predict ionic bonding quickly…

Ionic Bonding

= Ca3P2Formula Unit

This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance.

For an ionic compound, the smallest representative particle is called a: Formula Unit

Ionic Bonding

Cl-Na+

NaCl

Another example… both have single charges

Ionic Bonding

F-Mg2+

Mg F2

REMEMBERIf you want to predict ionic bonding quickly…

Ionic Bonding

O2-Ti4+

Ti O2

But be careful! It can be like balancing a fraction!TiO2, not Ti2O4

Peer-to-Peer Question #1 Draw the FORMULA UNIT for the

following atoms when they create an ionic bond:

– Mg and Cl

– Al and O

– K and Br

– Li and O

Properties of Ionic Compounds1. Crystalline solids - a regular repeating

arrangement of ions in the solid: Fig. 7.9, page 197

– Ions are strongly bonded together.– Structure is rigid.

2. High melting points Coordination number- number of ions

of opposite charge surrounding it

- Page 198

Coordination Numbers:

Both the sodium and chlorine have 6

Both the cesium and chlorine have 8

Each titanium has 6, and each oxygen has 3

NaCl

CsCl

TiO2

Do they Conduct? Conducting electricity means allowing charges

to move. In a solid, the ions are locked in place. Ionic solids are insulators. When melted, the ions can move around.3. Melted ionic compounds conduct.

– NaCl: must get to about 800 ºC.– Dissolved in water, they also conduct (free

to move in aqueous solutions)– Ex: Salt water conducts electricity but

WATER alone does NOT

- Page 198

The ions are free to move when they are molten (or in aqueous solution), and thus they are able to conduct the electric current.

Bellringer #58 (Jan 21st, 2011) Determine the formula and name for

when the following atoms combine to create IONIC COMPOUNDS:

– Ca and O

– Al and S

– K and N

Agenda (Jan 21st, 2011) Bellringer #58 Homework Check 2nd attempt distribution and discussion Review for Semester Exam Homework: Study Guide for EXTRA

CREDIT IF YOU PASS!!!!!!

– Extra study guide available on homework website…..VERY helpful!

Bellringer #59 (Jan 24th, 2011) Determine the electron configuration for

the following atoms:

– Phosphorous

– Fluorine

– Calcium

Bellringer #1 (Jan 31st, 2011) Name three things you know about ionic

compounds.

Agenda (Jan 31st, 2011) Bellringer #1 Discuss new semester Objective: Learn how to name ionic

compounds from transition metal ions Work on Chapter 7 Section

Assessment: pg. 207 #30-47 Hmwk: Cornell Notes 7.3 Mini Quiz Tomorrow

New Semester…..New Beginnings New Semester: Everyone starts all over again Starting at BR #1: Collecting BR #1-59

TOMORROW Late Work Policy: accept homework 1 DAY

LATE. Work MUST have a note on it as to WHY it is late and personally hand to Ms. Ingham.

Don’t wait too late to ask for help. This semester WILL BE harder than last.

Homework Board in back of room WILL BE updated.

Cornell Notes Cornell Notes MUST include the following for

COMPLETE credit:– Answer KEY CONCEPT questions.– Define ALL vocabulary in the section AND

give a picture and/or example.– Write notes for EVERY RED heading in the

section.– All notes MUST end with a brief summary

discussing the main points of the section. (If you take good notes, this should not be hard to do.)

Ionic Compounds With Transition Metals

The charges for transition metals are not as easy to predict as the metals from representative elements.– Ex: Copper can have a charge of 1+ or 2+

(Cu1+ or Cu2+) For this reason you MUST be given the

charge of the ion from a transition metal if you are going to create a ionic compound– Ex: Ti4+ and O

Ion ExamplesSymbol Name

Cu+ Copper (I) ion

Cu2+ Copper (II) ion

Fe2+ Iron (II) ion

Fe3+ Iron (III) ion

Pb2+ Lead (II) ion

Pb4+ Lead (IV) ion

Sn2+ Tin (II) ion

Sn4+ Tin (IV) ion

#1:Complete the table below (turn in at end of class).

Symbol Name

Cr2+

Chromium (III) ion

Mn2+

Manganese (III) ion

Cobalt (II) ion

Co3+

Predicting Ionic Compounds and Charges of Transition Metals

What Copper ion would create CuO?

What Copper ion would create Cu2O?

#2: Predict the ion that would create the compound below, then name the compound.

SnF2

SnS2

Fe2O3

What Next? Turn in questions #1 and #2 Begin work on pg.207 (unfinished work

is homework along with Cornell notes) Mini Quiz Tomorrow Bellringers #1-59 due TOMORROW

Bellringer #2 Write THREE things you know about

metals.

Agenda (Feb 1st, 2011) Bellringer #2 Homework Check 1st Semester BR Collection Write 7.3 Objectives 7.3 Overview Mini Quiz Hmwk: 7.3 Section Assessment #23-29

and Writing Activity

Section 7.3Bonding in Metals

OBJECTIVES:

–Model the valence electrons of metal atoms.

Section 7.3Bonding in Metals

OBJECTIVES:

–Describe the arrangement of atoms in a metal.

Section 7.3Bonding in Metals

OBJECTIVES:

–Explain the importance of alloys.

Metallic Bonds are…How metal atoms are held

together in the solid.Metals hold on to their valence

electrons very weakly.Think of them as positive ions

(cations) floating in a sea of electrons: Fig. 7.12, p.201

Sea of Electrons

+ + + ++ + + +

+ + + +

Electrons are free to move through the solid.

Metals conduct electricity.

Metals are MalleableHammered into shape (bend).Also ductile - drawn into wires.Both malleability and ductility

explained in terms of the mobility of the valence electrons

- Page 201

1) Ductility 2) Malleability

Due to the mobility of the valence electrons, metals have:

and

Notice that the ionic crystal breaks due to ion repulsion!

Malleable

+ + + ++ + + +

+ + + +

Force

Malleable

+ + + +

+ + + ++ + + +

Mobile electrons allow atoms to slide by, sort of like ball bearings in oil.

Force

Ionic solids are brittle

+ - + -+- +-

+ - + -+- +-

Force

Ionic solids are brittle

+ - + -

+- +-+ - + -

+- +-

Strong Repulsion breaks a crystal apart, due to similar ions being next to each other.

Force

Crystalline structure of metal (pg. 202)

If made of one kind of atom, metals are among the simplest crystals; very compact & orderly

Note Fig. 7.14, p.202 for types:1. Body-centered cubic:

–every atom (except those on the surface) has 8 neighbors

–Na, K, Fe, Cr, W

Crystalline structure of metal (pg.202)

2. Face-centered cubic:

–every atom has 12 neighbors

–Cu, Ag, Au, Al, Pb

3. Hexagonal close-packed

–every atom also has 12 neighbors

–different pattern due to hexagonal

–Mg, Zn, Cd

Alloys We use lots of metals every day,

but few are pure metals Alloys are mixtures of 2 or more

elements, at least 1 is a metal made by melting a mixture of the

ingredients, then cooling Brass: an alloy of Cu and Zn Bronze: Cu and Sn

Why use alloys? Properties are often superior to the pure

element Sterling silver (92.5% Ag, 7.5% Cu) is

harder and more durable than pure Ag, but still soft enough to make jewelry and tableware

Steels are very important alloys

– corrosion resistant, ductility, hardness, toughness, cost

More about Alloys… Table 7.3, p.203 – lists a few alloys Types? a) substitutional alloy- the

atoms in the components are about the same size

b) interstitial alloy- the atomic sizes quite different; smaller atoms fit into the spaces between larger

“Amalgam”- dental use, contains Hg