Quantum Mechanics - Solid State Physics - Lecture Slides, Slides of Solid State Physics

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1

Brief

Quantum Mechanics, Quantum Chemistry

& Molecular Physics

2

Issues & Ideas to Discuss

“An understanding of many of the physical properties of materials is predicated

on a knowledge of the interatomic forces that bind the atoms together.”

• Callister

We’ll start with a quick quantum mechanics & atomic-

molecular physics

(& chemistry!)

review

.

What causes chemical bonding

between atoms?

What types of bonds

are there?

In crystalline solids

,

What properties

of a material can be inferred from

understanding the bonding between atoms?

ENGR 215, September 2, 2008 – Page 4

What is an Electron?

Diffraction & Wave/Particle Duality

N

Young’s Double SlitExperiment

- Light

Young’s Double Slit

Experiment

- Electrons

Typical Diffraction

Pattern for Waves

Electron

Probability

Density

Electron

Orbit

ENGR 215, September 2, 2008 – Page 5

• The

Quantum Mechanics

of the atom

(

Schrödinger’s

Equation

)

describes electrons in terms of probability

distributions that can have only discrete values of energy.

N

Electron Orbitals: –

Probability Waves

The Shapes

of atomic

s, p, & d orbitals

are predicted by

Quantum Mechanics

(

Schrödinger’s Equation

)

ENGR 215, September 2, 2008 – Page 7

Each p orbital holds 2e- withopposite spins

Atomic Structure

ENGR 215, September 2, 2008 – Page 8

Each d orbital holds 2e- withopposite spins

Atomic Structure

ENGR 215, September 2, 2008 – Page 10

Chemistry SOL Review—Atomic Structure

The psuborbitals fill

The orbitals and the periodic table

ENGR 215, September 2, 2008 – Page 11

Chemistry SOL Review—Atomic Structure

The dsuborbitals fill

The orbitals and the periodic table

ENGR 215, September 2, 2008 – Page 13

Increasing energy

n=

n=

n=

n=

1s

2s 3s

3p 2p

4s

4p

3d

Note!!!

The

4s state

has a lower

energy than the

3d state

so the

N shell

begins to fill

before the

M shell

is filled.

Z

Element

Configuration

2

He

1s

2

10

Ne

1s

2

2s

2

2p

6

18

Ar

1s

2

2s

2

2p

6

3s

2

3p

6

36

Kr

1s

2

2s

2

2p

6

3s

2

3p

6

3d

10

4s

2

4p

6

N

Electronic Energy States

ENGR 215, September 2, 2008 – Page 14

Why? Their

Valence

(outer)

shell

is usually

not filled completely

.

In most elements, the electron configuration is

not stable

.

ElementHydrogenHeliumLithiumBerylliumBoronCarbon...NeonSodiumMagnesiumAluminum...Argon...Krypton

Atomic #

10111213 18 ...^36

Electron configuration1s

(^1)

1s

(^2)

(stable)

1s

(^2)

2s

(^1)

1s

(^2)

2s

(^2)

1s

(^2)

2s

(^2)

2p

(^1)

1s

(^2)

2s

(^2)

2p

(^2)

... 1s

(^2)

2s

(^2)

2p

(^6)

(stable)

1s

(^2)

2s

(^2)

2p

(^6)

3s

(^1)

1s

(^2)

2s

(^2)

2p

(^6)

3s

(^2)

1s

(^2)

2s

(^2)

2p

(^6)

3s

(^2)

3p

(^1)

... 1s

(^2)

2s

(^2)

2p

(^6)

3s

(^2)

3p

(^6)

(stable)

... 1s

(^2)

2s

(^2)

2p

(^6)

3s

(^2)

3p

(^6)

3d

(^10)

4s

(^2)

4

(^6)

(stable)

Adapted from

Table 2.2,

Callister 6e.

N

Atomic Electron Configurations for Some Elements

docsity.com

ENGR 215, September 2, 2008 – Page 16 Electronegativity:

A measure of reactivity, ranges from

0.

to

4.

Smaller Electronegativity

Larger Electronegativity

He

• Ne - Ar - Kr - Xe - Rn -

F

Cl

Br

I

At

Li 1.0Na0.

K 0.8Rb0.8Cs0.

Fr

H

Be1.5Mg1.2Ca1.0Sr1.0Ba0.9Ra0.

Ti

Cr1.

Fe1.

Ni

Zn1.

As2.

Large values:

A larger tendency to acquire electrons.

Adapted from Fig. 2.7,

Callister 6e.

(adapted from Linus Pauling,

The Nature of the

Chemical Bond

, 3rd ed, Copyright 1939 & 1940, 3rd edition. Copyright 1960, Cornell U.).

Electronegativity

N

ENGR 215, September 2, 2008 – Page 17

Because

electron configurations determine

how

(if)

various atoms will bond.

The type and strength of atomic bonds

determines material properties

.

A goal of this discussion

is to understand why

materials have the properties that they have.

So, we’ll now look at different ways that atoms can form interatomic

bonds, & consider the implications for material properties.

N

Why

have we been discussing all of this about electrons?

ENGR 215, September 2, 2008 – Page 19 One or two (or more) electrons are transferred from an atom

that has extra valence electrons to one that lacks them.

Give up electrons

Acquire electrons

He

• Ne - Ar - Kr - Xe - Rn -

F 4.0Cl3.0Br2.

I 2.5At2.

Li 1.0Na0.

K 0.8Rb0.8Cs0.7Fr0.

H

Be1.5Mg1.2Ca1.0Sr1.0Ba0.9Ra0.

Ti

Cr1.

Fe1.

Ni

Zn1.

As2.

CsCl NaClMgOCaF

O

For 2 atoms to form an ionic bond,

a large electronegativity difference is required.

N

Examples: Ionic Bonding

ENGR 215, September 2, 2008 – Page 20

Na (metal)

unstable

Cl (nonmetal)

unstable

electron

CoulombicAttraction

Na (cation)

stable

Cl (anion)

stable

This electron transfer leaves both atoms ionized, withopposite charges. They are then strongly attracted toeach other through the

Coulomb

attraction:

Example:

NaCl

Ionic Bonding

N