When heated to high temps, gases give off light.If this light is passed through a slit, then through aprism or diffraction grating, the following patterns are seen:

bright-linespectrum

dark-linespectrum

Why are there only separate (discrete) colors or lines?

the lines are images of the slits

Or if a light with a continuous spectrum is passed through a cold gas and then through a prism, you get:

Models of the atom:

I. _____________________: In 1897, discovered e-’s were

________ mass and ____________________ charged. Since

he also knew that atoms as a whole were ______________,

he developed the ______________________________ model:

negative e-

are the

____________

positive charge is ________________

distributed in a___________________

“raisin/plum pudding”

J.J. Thomson

low negativelyneutral

One _________ :atom

uniformly “pudding”

raisins

phosphorescentscreen

One of JJ's experimentswith electrons:

battery

Which side of the battery was positive?

electron beam

_____________________ : In 1909, he fired ___________

particles (positively charged ____________ nuclei) at thin

gold foil:

particle

Au foil

only 1 in 8000 were

scattered ____________

________ were not

scattered or were

scattered through

_____________ anglesHis conclusion:

The ___________________________ mass is concentrated in

_________________________ at the atom's _____________ .

He called this the ________________ of the atom.

Rutherford alphahelium

most

backwards

positively charged

a very small volume

only small

centernucleus

II. As a result of Rutherford's experiment, the

___________________ model was developed:

The e-'s ___________ the nucleus similar to how

________________ orbit __________________ .

______________charge

concentrated in the

_____________

size of nucleus ~ ___________________ of

` the diameter of atom

positive

orbit

1/10,000

solar system

planets the Sun

e-

e-

nucleus

One atom:

_____________________with the solar system model: 1. Circular orbital motion q _________________

2. Accelerating q ______________emitted from atom

3. Energy radiated orbits will _____________________

4. All atoms should ___________________in a short time

5. As they collapse, the e- should______________________

and the atom should _____________________emit a higher

and higher ______________________ of light

6. This should produce a ____________________spectrum.

but _______________ spectra were observed.

accelerates

radiation

get smaller

collapse

revolve faster

Problems

continuouslyfrequency

continuousdiscrete

But only saw:

Why?

Should see:

III. The Bohr model for ___________________: 1. The 1 e- in H____________________ or ______________________the nucleus. It __________ in a ___________.2. The e- can only be found at ______________ (certain specially allowed) distances, which are unfortunately still called __________________ . Each orbital has a _____________ number,____ . a/ The orbital _____________to the nucleus is called the ____________________and has n = ____. It has the ______________ energy = ______________.

b/ The orbital furthest from the nucleus has the ______________energy and has n =_____. The energy

of that orbital = ____. In that case, the e- is said to be _______________ , which means it is ________________ from the atom completely.

hydrogen, H

does not orbitaround

discrete

move

“orbitals.”

nquantum

ground state

exists "state"

closest

1lowest -13.6 eV

highest ∞

ionized.

0removed

n=1

n=2

n= ∞

etc…

e- is___________

_________state ofelectron

n=3

The ______ e- can be foundat ______ level

A. Bohr model of H atom:

n= 2 to ∞ are called____________ states

proton

----- = _____________orbitals

ground

ionized

“excited”one

any

If an e- moves from to a ___________ energy orbital to a __________one, a photon of light is ___________ (given off).

The ____________ of the emitted photon: Eph =

n=1

n=2

n=3

photon_________

B. Photon _________________ :emission

lowerhigher

emitted

Ei - Efenergy

emitted

Ei =

Ef =

Eph =

Easy way: IGNORENEG. SIGNS AND JUSTSUBTRACT!!!

Eph =

=

Eph = Ei – Ef

E3=

E2 =

E3 – E2

3.40 – 1.51

1.89 eV

Reference Tables: page 3, top left.

-1.51 eV

-3.40 eV

=

– 1.51 – (-3.40)

The __________ of the absorbed photon: Eph =

photon_________

If an e- moves from a ___________ energy orbital to a __________one, a photon of light is ___________ (taken in).

C. Photon _________________ :absorption

lower

higher absorbed

Ei - Ef

n=1

n=2

n=3

energy

absorbed

Ef =

Ei =

Eph =

Eph =

=

Eph = Ei – Ef

E3 = -1.51 eV

E1= -13.60 eV

E1 – E3

(ignore neg. signs)

13.60 – 1.51

12.09 eV

D. Energy ____________________:

atom

Atom __________ energy

as e- moves __________

photon

___________

___________

Emission (the ____________of light):

Absorption (the ____________ of light):

atom

Atom _________energy

as e- moves_________

photon

__________

__________

conservation

birth

death

loses

down

removesenergy

bringsenergy

gains

up

In both cases: _________________ = ___________________energy gained energy lost

2. No _______________________ jumps are allowed!!!

Only jumps from one ______________energy level or

orbit to another ____________ energy level are

allowed.3. That is why _______________________ energy photons

can be emitted or absorbed by atoms..

4. Since Eph = hf, only certain __________________(colors)

are produced.

5. That is why photon energies

are ___________________(only

certain values are allowed).

1. The technical term for “jumps” is____________________.

E. NOTES:transitions

“inbetween”

allowed

allowed

only certain

frequencies

“quantized”

Bigger e- jumps more (transitions) more _________

_____________ frequency photons

in ___________________ and beyond

Eph = Ei – Ef = hf

Little e- jumps less _________

(transitions) less _________ _____________ frequency photons

in ____________________ and lower

ΔE= amount of e-____________"jump"

ΔEEph

blue, violet, UV

ΔE

Eph

higher

red, IRlower

This is true for _______________ and _______________ .emission absorption

high f low f

BIG jumpslittle jumps

_______ transitions

_______energy light

involv

e

_______ transitions

_______energy light

involv

elittle

low

big

high

Which transitions involve visible light? to the n=2 level

Where would thesephotonsappear in thespectrum?

Andthese?

F. ________________ : Jumps from any level to n = ___ will___________the e- from the atom.

Ionization _________________:The _____________required to ___________an e- from an atom.

What is the ionization potential for a H atom thathas an electron in the groundstate?

What is the ionization potential for a H atom thathas an electron in the n=3state?

13.6 - 0= 13.6 eV

1.51 - 0= 1.51 eV

Ionization ∞

remove

potentialenergy

remove

Notice: Mercurygas also has a fun diagram!

But mercury hasletters instead of numbers.

G. So where do _________________ (bright line) and _____________________spectra come from?

The missing colorsare the __________ onesthat were_____________by the gas.The heated gas

absorbs, then emitsonly those photonsfrom _____________energy transitions.

absorptionemission

Unless the source is a low-density gas, interactions with otheratoms blur the lines into a _________________spectrum.

allowed

continuous

absorbed

same

The same transitions produce same lines:

photon absorbed

photon emitted

same transition

•Each element has a _____________electron structure.•The electrons make _______________transitions.•Each transition produces a spectral ___________.•The set of lines is a __________________for that element.

Ex: Atomic absorption spectroscopy:

white light

gas orliquid

containing______________

elements that absorb

certain photons

slit

_________:disperseslight

___________

spectrum

uniqueunique

line

fingerprint

unknown

prism

absorption

Sun

The Sun produces a continuous spectrum b/cthe interaction of many gases blurs the energy levels.

Atmosphere of Sun – absorbsonly photons that can “jump” levels of gases in it. That is how helium was discovered.

light after passingthrough atmosphereproduces a dark linespectrum

Stars broad lines dense gas compact star red shifted star moving away blue shifted star approaching

incr

easi

ng

tem

pera

ture

V. Bohr’s model could NOT explain why e- could onlyhave ______________orbitals and energies. This was later explained by_________________________:

The e- acts like a __________ and __________________interferes with ___________ as it wraps itself around the ________________:

This can only occur at certain ______________ distances from the nucleus.

Louis DeBroglie

constructively

nucleus

itself

discrete

discrete

nucleus

electron________

wave

orbits

The electrons form “standing waves” around the nucleus.

Electrons can act like waves. The wavelength’s of e- depend on their speed, but they are generally very small. That allows us to take pictures of very small things.

fruit fly

colorized house fly

surface of poison ivy

VI. The ___________Model:

1. The electron is described by a ________ function, .”

2. The square: 2is the ___________________ of finding

an electron at a certain position. The e- is most likely to

be found where the "probability cloud" is ________________

3. The electron is no longer thought to be located at

a ________________ location, but may be ______________ .

4. The locations of highest probability correspond

to the positions of the old________________________.

Cloud

probability

_________ orbitals:

wave

definite

densest

spread out

Bohr orbits

_________ clouds

Bohr probability

Mass has a dual nature: particles or waves.

Light has a dual nature: particles or waves.

mass usuallyacts like aparticle

mass sometimesacts like a wave

light usuallyacts like awave

light sometimesacts like aparticle