This stuff is really weird…

Mind Map Notes

Modern Atomic Theory

Preamble - Before Atomic

Theory Problems and

Conflicts

Transition

Ideas

I’m tired…

knew that there was a negative particle in the atom but where is it???

Which Experimenter? Review• Model of atom was dense mass

(protons) in center with electrons around it.

• This model had some serious problems.

• Why doesn’t the nucleus fly apart?

• Why aren’t the electrons attracted to the nucleus?

Like charges REPEL!

Opposite charges ATTRACT!Nuclear Model

Mind Map Notes

Modern Atomic Theory

Preamble Before

Atomic Theory

Thom

pson

Disc

over

s

Electro

n bu

t doe

sn’t

know

whe

re it

isRuthe

rford

disc

over

s nuc

leus

and

prot

on

Before Atomic Theory

• Light was considered a wave

• All waves must travel through a “medium” (like water)

• The universe was filled with a substance called “Ether” that light traveled through

BACKGROUND - The Wave Nature of Light

• Wavelength – How far apart the waves are

• Frequency– How fast the waves travel

• Wavelength and Frequency are related• Wavelength and Frequency are

DIRECTLY related to amount of ENERGY in the light.

Light is “Electromagnetic Radiation” MEANS - a form of energy that exhibits wave like characteristics

Wavelength and Frequency

• Not Working very hard

• Long Wavelength

• Low Frequency

Wavelength and Frequency

• Working VERY hard

• Short Wavelength• High Frequency

What does this tell you about the relationship between wavelength, frequency and energy?

Wavelength and Frequency are “INVERSELY PROPORTIONAL”

Energy and Light

Which colors of light have the greatest energy?

Which colors of light have the least energy?

How do you know?

Greatest - Violet, blue, x-rays

Least - Red, orange, infrared, radio waves

Long wavelengths use less power to generate.

Before Atomic Theory

• Light was considered a wave

• All waves must travel through a “medium” (like water)

• The universe was filled with a substance called “Ether” that light traveled through

Photoelectric Effect: Problems & Conflicts

• In the early 1900s an experiment was done that COULD NOT be explained by light being a wave.

• Different colors were shined on to a metal plate

• Electrons would come off the metal plate for ONLY CERTAIN FREQUENCIES OF LIGHT (colors)

If light was a “wave” ANY frequency of light would ALWAYS cause electrons to be released.

Brick Wall Analogy

• Different balls thrown at wall

• Each one with different mass

• All at same speed of 90 mile/hour

• Each ball is like a color or light - each has its own energy

Ping Pong Ball

No effect

Softball

No effect

Super Dense Steel Ball

Dislodges Brick and send it flying

Mind Map Notes

Modern Atomic Theory

Preamble

Thom

pson

Disc

over

s Elec

tron

but d

oesn

’t kn

ow w

here

it is

Ruthe

rford

disc

over

s

nucle

us an

d pr

oton

Light

was

cons

ider

ed a

wave

and

trave

led th

roug

h “E

ther

”Problem

s and Conflic

ts

Photo Electric Effect conflicts

with understanding of light

Differen

t colors

(frequencie

s) of

light c

aused

differen

t responses

New Idea - Einstein and the Photoelectric Effect

• This observation led Einstein to believe that light acted like a particle and a wave

• This is called the “dual nature” of light

Mind Map Notes

Modern Atomic Theory

Preamble

Thom

pson

Disc

over

s Elec

tron

but d

oesn

’t kn

ow w

here

it is

Ruthe

rford

disc

over

s

nucle

us an

d pr

oton

Light

was

cons

ider

ed a

wave

and

trave

led th

roug

h “E

ther

”Problem

s and Conflic

ts

Photo Electric Effect conflicts

with understanding of light

Differen

t colors

(frequencie

s) of

light c

aused

differen

t responses

Tran

sitio

n Id

eas

Einstein says light

has “dual nature”

Plank and the Photoelectric Effect

This was the basis of “Quantum Theory”

Maxwell Plank suggested that because energy was NOT being given off continuously, he suggested that little “packets” of energy called ‘quanta” were being given off.

Line Emission Spectrum Observations

• Experiments were conducted on different elements

• Different elements were observed to produce different colors (or frequencies) when supplied with energy

Identifying Elements with Flame Tests

Na K Li Ba

Energy - 3 Categories - Review• Potential Energy

– Position– In Chemistry - the position of

atoms with respect to each other• Kinetic Energy

– Movement– In Chemistry - heat, molecules

moving• Radiation

– Electromagnetic Spectrum– In Chemisty - radiation and light

Electrons and the Atom

Nucleus

Electron at “Ground State”

e-

Add Energy

e-

electron at “Excited State”

Electron at “Ground State”

e-

Just like a jumper has potential energy at the top of the jump, the electron has stored potential energy in the higher orbit.

Quantum Leap

Electrons disappear from one orbit and reappear at another without visiting the space in between!

Release Energy in the form of colored light

Neils Bohr and the Planetary Model of the Atom

• Bohr hypothesized that electrons could only be at certain energy “levels”

• Electrons could “jump” from lower to higher energy states or higher to lower

• Specific frequencies result in specific colors for each element.

Quantum Levels

• Each energy level is given a number (quantum number)

• When an electron goes from one quantum level to another, it gives off a specific amount of energy that will produce a specific frequency and wavelength (colored light)

If you Think This is Hard to Understand…

A person who wasn’t outraged on first hearing about quantum theory doesn’t understand what had been said…

Neils Bohr

Until it is observed an electron must be regarded as being “at once everywhere and nowhere”

This is “an area of the universe that our brains aren’t wired to understand.”

Dennis Overbye,scientific commentator

James Trefil,

Scientific Author

Things on a small scale behave nothing like things on a large scale.

Mind Map Notes

Modern Atomic Theory

Preamble

Thom

pson

Disc

over

s Elec

tron

but d

oesn

’t kn

ow w

here

it is

Ruthe

rford

disc

over

s

nucle

us an

d pr

oton

Light

was

cons

ider

ed a

wave

and

trave

led th

roug

h “E

ther

”Problem

s and Conflic

ts

Photo Electric Effect conflicts

with understanding of light

Differen

t colors

(frequencie

s) of

light c

aused

differen

t responses

Tran

sitio

n Id

eas

Einstein says light

has “dual nature”

Bohr’s Model of the Atom

(planetary), Electrons at only

certain levelsPlank’s “Quanta”

Line Emission

Spectrum

Showed electrons could only

be at certain energy levels

How am I Supposed to Remember this Stuff?

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

I was riding along in my Rather have a Ford, with the gold foil wrapped plum pudding in the back…(Rutherford)

When I hit a brick wall… (analogy)

Of course at an accident, you always take a photo… (photoelectric effect)

But nothing happened, so it was boring…(Bohr)

However, I did see some colors, which was exciting… (line emission spectrum)

At that point I had a lot of questions… (Q is for Quantum Theory)

And I was uncertain as to what to do… (Heisenberg Uncertainty Principle)

If you turn it sideways you can see the levels…

• Einstein first suspected the fallacy of Ether when he was 15.

• He wrote his first paper on this theory and sent it to his uncle

• In 1881 and 1887 the Michelson Morely experiment proved Ether did not exist.

Einstein! Quit looking out the window! You need to do your math!

Of course Ether exists, you silly boy! All scientist agree!

• Bohr postponed his honeymoon to write his paper

• We consider the “planetary model” to be created by Bohr but actually a Japanese physicist named Hantaro Nagaoka did in 1904 - too bad it was TOTALLY WRONG!