Recent Atomic Models Max Planck - PowerPoint Presentation

Slide1

Recent Atomic Models

Max Planck (1900): Proposed thatamounts of energy are quantized



only certain

E values are allowed

Niels Bohr (1913): e– can possess only certain amounts of energy, andcan therefore be only certain distances from nucleus.

e

–

found

here

e

–

never

found here

planetary

(Bohr) model

NSlide2

Continuous vs. Quantized Energy

Energy

A B

Zumdahl, Zumdahl, DeCoste,

World of Chemistry

2002, page 330

continuous quantizedSlide3

Bohr Atom

The Planetary Model of the AtomSlide4

Bohr’s Model

Nucleus

Electron

Orbit

Energy LevelsSlide5

ENERGY

(HEAT, LIGHT,

ELEC., ETC.)

Light

When all e

–

are in lowest possible energy state,

an atom is in the

____________

.

ground state

e.g.,

He: 2 e

-

, both in 1

st

energy level

If “right” amount of energy is absorbed by an e

–

, it can

“jump” to a higher energy level. This is an unstable,

momentary condition called the ____________.

excited state

e.g.,

He: 1 e

-

in 1

st

E level, 1 e

-

in 2

nd

E level Slide6

When e–

falls back to a lower-energy, more stableorbital (it might be the orbital it started out in, but itmight not), atom releases the “right” amount ofenergy as light.

EMITTED LIGHT

Any-old-value of energy to be

absorbed or released is

NOT OK. This explains

the lines of color in an

emission spectrum

.

Slide7

Frequency A

Frequency B

Frequency C

n

= 2

n

= 1

n

= 3

NSlide8

1

ST

E.L.

2

ND

E.L.

3

RD

E.L.

4

TH

E.L.

5

TH

E.L.

6

TH

E.L.

Lyman

(UV)

Paschen

(IR)

Balmer

(visible)

~

~

~

~

~

~Slide9

Continuous and Line Spectra

4000 A

o

5000

6000

7000

light

Na

H

Ca

Hg

400 450 500 550 600 650 700 750 nm

Visible

spectrum

l

(nm)Slide10

Flame Emission Spectra

Photographs of flame tests of burning wooden splints soaked in different salts.Include link to web page

http://www.unit5.org/christjs/flame%20tests.htm

methane gas

wooden splint

strontium ion

copper ion

sodium ion

calcium ionSlide11

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.Slide12

Fireworks

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.Slide13

electromagnetic radiation (i.e., light)

--

--

E

B

waves of oscillating electric (E)

and magnetic (B) fields

source is…

vibrating electric charges

Slide14

Characteristics of a Wave

frequency

: the number of cycles per

unit time (usually sec)

amplitude

A

crest

wavelength

l

trough

--

unit is Hz, or s

–1

or 1/sSlide15

radio waves

IR

visible

UV

X-rays

gamma rays

cosmic rays

electromagnetic spectrum

: contains all of the “types” of

light that vary according to frequency and wavelength

R

O

Y

G

BV

large

l low f low energy

small

l

high f

high energy

-- visible spectrum ranges from

only ~400 to 750 nm (a very

narrow band of spectrum)

microwaves

400 nm

750 nm Slide16

Increasing wavelength

Increasing frequency

Increasing energySlide17

Some light humor…Slide18

Waves

Low

frequency

High

frequency

Amplitude

Amplitude

long wavelength

l

short wavelength

l

Both travel at the same speed…the speed of light!Slide19

Waves

Low

frequency

High

frequency

Amplitude

Amplitude

long wavelength

l

short wavelength

l

60 photons

162 photons

Low

energy

High energySlide20

Red and Blue Light

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 325

Photons

- particle of light that carries a quantum of energySlide21

Albert Michelson (1879)

--

first to get an accurate

value for speed of light

The speed of light in

a vacuum (and in air)is constant:

c = 3.00 x 10

8

m/s

c = f

l

-- Equation:

Albert Michelson

(1852–1931)

c = 671 x 10

6 mph Slide22

E = h f

In 1900, Max Planck assumed

that energy can be absorbed

or released only in certaindiscrete amounts, which hecalled quanta.

Later, Albert Einstein dubbeda light “particle” that carried a

quantum of energy a photon. -- Equation:

E = energy,

h = Planck’s constant

in J

= 6.63 x 10

–34

J∙s (i.e., J/Hz)Max Planck(1858–1947)

Albert Einstein

(1879–1955)Slide23

A radio station transmits

at 95.5 MHz (FM 95.5).Calculate the wavelengthof this light and the energyof one of its photons.

c = f

l

= 3.14 m

E = h f

= 6.63 x 10

–34

J/Hz (95.5 x 10

6

Hz)

= 6.33 x 10

–26

J

3.00 x 10

8

m/s

=

95.5 x 10

6

HzSlide24

quantum mechanical model

electron cloud model

charge cloud model

Schroedinger

, Pauli, Heisenberg, Dirac (up to 1940):According to the QMM, we never know for certain where the e

– are in an atom, but the equations of the QMM tell us the probability that we will find an electron within a certain distance from the nucleus. Slide25

Electron Cloud Model

Orbital (“electron cloud”) instead of “orbits”Region in space where there is 90% probability of finding an electron…creates unique 3-D shapes

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Electron Probability vs. Distance

Electron Probability (%)

Distance from the Nucleus (pm)

100

150

200

250

50

0

0

10

20

30

40

Orbital

90% probability of

finding the electronSlide26

Models of the Atom Review

Dalton’s model

(1803)

Thomson’s plum-pudding

model (1897)

Rutherford’s model

(1909)

Bohr’s model

(1913)

Charge-cloud model

(present)

Dorin, Demmin, Gabel,

Chemistry The Study of Matter

, 3

rd

Edition, 1990, page 125

Greek model(400 B.C.)

+

-

-

-

-

-

e

e

e

+

+

+

+

+

+

+

+

e

e

e

e

e

e

e

"In science, a wrong theory can be valuable and better than no theory at all."

- Sir William L. BraggSlide27

Models of the Atom Timeline

Dalton’s model

(1803)

Thomson’s plum-pudding

model (1897)

Rutherford’s model

(1909)

Bohr’s model

(1913)

Charge-cloud model

(present)

Dorin, Demmin, Gabel,

Chemistry The Study of Matter

, 3

rd

Edition, 1990, page 125

Greek model(400 B.C.)

1800 1805 ..................... 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945

1803

John Dalton

pictures atoms as

tiny, indestructible

particles, with no internal structure.

1897

J.J. Thomson, a British

scientist, discovers the electron,

leading to his "plum-pudding"

model. He pictures electrons

embedded in a sphere of

positive electric charge.

1904

Hantaro Nagaoka, a

Japanese physicist, suggests

that an atom has a central

nucleus. Electrons move in

orbits like the rings around Saturn.

1911

New Zealander

Ernest Rutherford states

that an atom has a dense,

positively charged nucleus.

Electrons move randomly in

the space around the nucleus.

1913

In Niels Bohr's

model, the electrons move

in spherical orbits at fixed

distances from the nucleus.

1924

Frenchman Louis

de Broglie proposes that

moving particles like electrons

have some properties of waves.

Within a few years evidence is

collected to support his idea.

1926

Erwin Schr

ö

dinger

develops mathematical

equations to describe the

motion of electrons in

atoms. His work leads to

the electron cloud model.

1932

James

Chadwick, a British

physicist, confirms the

existence of neutrons,

which have no charge.

Atomic nuclei contain

neutrons and positively

charged protons.

+

-

-

-

-

-

e

e

e

+

+

+

+

+

+

+

+

e

e

e

e

e

e

eSlide28

Shapes of s, p, and d-Orbitals

each holds 2 electrons (s2)

e

ach of 5 orbitals holds 2 e - = 10 total d electrons (d10)

each of 3 orbitals holds 2 e - = 6 total p electrons (p6)Slide29

f-orbitals

each of 7 orbitals hold 2 e- = 14 e-How many “g-orbitals” could exist and how many e- could they hold?Slide30

theoretical g-orbitals

each of 9 orbitals hold 2 e- = 18 e-Slide31

Relative Sizes 1s and 2s

1s 2s

Zumdahl, Zumdahl, DeCoste,

World of Chemistry

2002, page 334Remember: s, p, d, and f refer to the orbital shapeAs you add more e-, progressively larger orbitals are needed to accommodate all the of e- Slide32

Copyright

© 2006 Pearson Benjamin Cummings. All rights reserved.

Orbitals overlap each other as you get farther from the nucleus

Orbital Filling VideoSlide33

s, p, and d-orbitals overlap

s orbitals:

Each holds 2

electrons

(outer orbitals ofGroups 1 and 2)

p orbitals:

Each of 3 sets holds 2 electrons = 6 electrons

(outer orbitals of Groups 3 to 8)

d orbitals:

Each of 5 sets holds

2 electrons

= 10 electrons(found in elements in third periodand higher)Slide34

s block

p block

d block

f

block

6

7

Periodic Patterns

1

s

2

s

3

s

4

s

5

s

6

s

7

s

3

d

4

d

5

d

6

d

1

s

2

p

3

p

4

p

5

p

6

p

7

p

4

f

5

f

1

2

3

4

5

6

7

(n-1)

(n-2)

nSlide35

Sections of Periodic Table to Know

f-block

s-block

d-block

p-blockSlide36

Energy Level Diagram of a Many-Electron Atom

Arbitrary

Energy Scale

18

18

32

8

8

2

1s

2s 2p

3s 3p

4s 4p 3d

5s 5p 4d

6s 6p 5d 4f

NUCLEUS

O’Connor, Davis, MacNab, McClellan,

CHEMISTRY Experiments and Principles

1982, page 177

Each orbital can only hold 2 e-

Start from the bottom and add e-Slide37

You don’t have to memorize the order…just start at the beginning and fill in e-…Slide38

s-block

1st Period (row)

1s

1

1 e- in “1s” orbital

Periodic Patterns

Example -

Hydrogen

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chemSlide39

Writing Electron Configurations:

Where are the e–? (probably)

As

H

He

NAl

Li

Ti

Xe

1s

2

2s2

3p6

2p64s

23d10

3s

24p6…1s1

1s

2

1s

2

2s1

1s2

2s2

2p

3

1s

2

2s

2

3p

1

2p

6

3s

2

1s

2

2s

2

3p

6

2p

6

4s

2

3d

2

3s

2

1s

2

2s

2

3p

6

2p

6

4s

2

3d

10

3s

2

4p

3

1s

2

2s

2

3p

6

2p

6

4s

2

3d

10

3s

2

4p

6

5s

2

4d

10

5p

6

Filling OrderSlide40

Notable e- configuration exceptions:

Cu

Cr

1s

2

2s23p6

2p

6

4s

1

3d

53s21s2

2s2

3p62p6

4s1

3d

103s2Mo and W (theoretically Sg) will behave similarly to CrAg and Au (theoretically Rg) will behave similarly to Cu

Why? Generally, full orbitals and half-filled orbitals have lower energies and are thus more stable. So, while we might expect Cr to end with 4s

23d4, promoting an s e- to the d orbitals creates two half-filled shells.Slide41

[Ar]

4s

2

3d

10

4p2

Periodic Patterns

Example -

Germanium

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Ge

72.61

32Slide42

Electron Configuration Battleship

(your shots)Slide43

Electron Configuration Battleship

(your ships and opponent’s shots)Slide44

S

Shorthand Electron Configuration (S.E.C.)

To write S.E.C. for an element:

1. Put symbol of noble gas that precedes

element in brackets.

2. Continue writing e– config. from that pointCo

In

Cl

Rb

[ Ne ]

3s

2 3p4 [ Ar ]

4s2 3d7

[ Kr ]

5s2 4d10 5p1

[ Ne ] 3s2 3p5 [ Kr ]

5s

1

Ge

72.61

32Slide45

Shorthand Configuration Review

[Ar] 4

s

2

Electron configuration

Element symbol

[Ar] 4

s

2

3

d

3

[Rn] 7

s

2

5

f

14

6

d4

[He] 2

s

2

2p5

[Kr]

5

s

1

4

d

10

[Kr] 5

s

2

4

d

10

5

p

5

[Kr] 5

s

2

4

d

10

5

p

6

or [Xe]

[He] 2

s

2

2

p

6

3

s

2

3

p

6

4

s

2

3

d

6

Ca

V

Sg

F

Ag

I

Xe

Fe

[Ar] 4

s

2

3

d

6Slide46

Periodic Patterns ReviewPeriod # (1-7) primary energy level (n) (subtract for d & f)

Group # (1-8…excluding d block) total # of valence e-Column within Sublevel block # of e- in sublevel

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chemSlide47

Three Principles about Electrons

aufbau Principle:

for equal-energy orbitals (p, d)

each must have one e–

beforeany take a second

Pauli Exclusion Principle:e– will fill the lowest-energyorbital available

Hund’s

Rule

:

two e–

in same orbitalhave different spins

1s22s23p

62p6

4s2

3d10…

3s

2Friedrich Hund

Wolfgang PauliSlide48

General RulesAufbau Principle Electrons fill the lowest energy

orbitals first. “Lazy Tenant Rule”Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

2

s

3

s

4

s

5

s

6

s

7

s

1

s

2

p

3

p

4

p

5

p

6

p

3

d

4

d

5

d

6

d

4

f

5

f

1

s

2

s

2

p

3

s

3

p

4

s

4

p

3

d

4

d

5

s

5

p

6

s

7

s

6

p

6

d

4

f

5

f

5

d

Energy

NO ELEVATOR!Slide49

General Rules

Hund’s

Rule

Within a sublevel, place one electron per orbital before pairing them.

“Empty Bus Seat Rule”

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

2p

2p

ORSlide50

General RulesPauli Exclusion Principle Each orbital can only hold TWO electrons and the must have opposite spins.

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Wolfgang Pauli

1sSlide51

O

Orbital Diagrams

…show spins of e

– and orbital location

1s

2s

2p

3s

3p

1s

2s

2p

3s

3p

P

1s

2

2s

2

2p

4

1s

2

2s

2

2p

6

3s

2

3p

3Slide52

HAVE MORE

ENERGY

ARE FURTHER

FROM NUCLEUS

AND

The Importance of Electrons

orbitals

:

In a generic e

–

config (e.g., 1s

2 2s2

2p6 3s2 3p6…):

regions of space where an e– may be found

# of energy level # of e

– in those orbitals

coefficient

superscript

In general, as energy level # increases, e

–

…Slide53

Shorthand Configuration

S 16e

-

Valence Electrons

(Highest energy level)

Kernel (Core) Electrons

S 16e

-

[Ne]

3s

2 3p4

1s2

2s2

2p6

3s

23p4Electron ConfigurationLonghand Configuration

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

S

32.066

16Slide54

INVOLVED IN

CHEMICAL

BONDING

kernel (core) electrons

:

valence electrons:

in inner energy level(s);

close to nucleus

in outer energy level

He:

Ne:

Ar:

Kr:

1s

2

[ He ] 2s2 2p6 [ Ne ] 3s2

3p6

[ Ar ] 4s2 3d10 4p

6

Noble gas atoms have FULL valence orbitals. They are stable, low-energy, and unreactive.

(2 valence e–)

(8 valence e–)

(8 valence e

–

)

(8 valence e

–

) Slide55

octet rule:

the tendency for atoms to fill valence orbitals completely with 8 e– (outer E level)

Other atoms “want” to be like noble gas atoms…

doesn’t apply to He, Li, Be, B (which require 2)

or to H (which requires either 0 or 2)…“duet rule”

fluorine atom, F 9 p+, 9 e–

** So, they lose or gain e

–

...

gain 1 e–

or lose 7 e-

? 9 p+, 10 e– F is more stable asan F– ion

F

–

chlorine atom, Cl

17 p+

, 17 e– 17 p+, 18 e– Cl is more stable asa Cl– ion

Cl

–

How to be like

a noble gas…?

[He] 2s

2

2p

5

[Ne] 3s

2

3p

5

gain 1 e

–

or lose 7 e

-

? Slide56

lithium atom, Li

3 p+, 3 e–

lose 1 e

– or gain 7 e-?

3 p+, 2 e–

Li is more stableas the Li+ ion.

Li

+

sodium atom, Na

11 p

+

, 11 e– lose 1 e– or gain 7 e-?

11 p+, 10 e–

Na is more stableas Na+

ion

Na

+How to be likea noble gas…?

[He] 2s

1

[Ne] 3s

1Slide57

1+

Know charges on these columns of Table:

Group 1:

Group 2:

Group 3:

Group 5:

Group 6:

Group 7:

Group 8:

2+

3+

3–

2–

1–

0

1+

2+

3+

3–

2–

1–

0

…also called oxidation numbers. Slide58

s

p

d

f

6

7

Periodic Patterns and Charge Trends

1

s

1

2

3

4

5

6

7

+1

+2

(n-2)

n

+3

- 3

- 2

- 1

Variable ChargeSlide59

Naming Ions

e.g., Ca2+

Cs

+

Al3+

Cations use element name and then say “ion”

e.g., S

2–

P

3–

N

3–O2–Cl–

Anions

change ending of element name to “ide”and then say “ion”

calcium ion

cesium ion

aluminum ionsulfide ion

phosphide ion

nitride ion

oxide ion

chloride ion