1. Why is the energy in an atom said to be quantized?

Question of the Day

Day 4 1-4

If a light wave has a frequency (ν) of 3.0 * 1015 Hz, what is its wavelength?

1.0 * 10-7

m

REVIEW

2. Who demonstrated photons can move electrons?

ComptonAHHHH!

The relationship between frequency , wavelength (), and color to the energy of light: ,

Color: red = low E, violet = high E

E : many photon punchesE: big gaps between consecutive photons.

Color: red = low E, violet = high E

each color has its own energy

color = type of light

The Effects of Different Photons:Microwaves: can’t feel

Infrared: feel with skin, warms or burns.Visible light: see with eyes, heats when absorbed.Ultraviolet: can’t feel or see, affects cells – freckles, tan, burn, cataracts.

X-rays: can’t feel or see, pass through body, but absorbed by bones and dense matter.Gamma rays: can’t see or feel, affects cells, causes mutations in cells and molecules.

The Effects of Different Photons:Ultraviolet: can’t feel or see, affects cells – freckles, tan, burn, cataracts.

Neils BohrTried to explain

why each element has its own unique (bright) line(bright) line spectrumspectrum. He studied HH.

Using previous discoveries- Bohr hypothesized that an atom’s electrons are located in specific energyspecific energy levelslevels. Each energy level, aka orbitorbit or shellshell is a set distance from the atom’s nucleusnucleus. …

… Electrons jumpjump or fallfall from one energy level to another, while simultaneously gaining or losing energyenergy. Electrons are not permitted to stop betweenbetween energy levels.

Neils Bohr… Each energy

level, aka orbitorbit or shellshell. Is a set distance from the atom’s nucleusnucleus. …

Bohr’s Hypothesis•In the line spectrum of an In the line spectrum of an atom, Bohr saw specific atom, Bohr saw specific colorscolors..

•Each specific Each specific colorcolor has a has a specific specific energyenergy..

•That specific amount of That specific amount of energyenergy is related to a is related to a specific specific distancedistance from the from the nucleus.nucleus.

Ground vs. Excited States:An atom is in the groundground state when

its electrons fill the lowest possible energy levels that are closestclosest to the nucleus. This is when the atom is most stablestable.An electron can gaingain energy and jumpjump to a higher energy level. The electron must absorb an exact exact amountamount …

An electron can gaingain energy and jumpjump to a higher energy level. The electron must absorb an exact exact amountamount … of energy to make a jump to a specific energy level. The energy that the electron gains comes from a photonphoton.

Ground vs. Excited States:

When an atom’s electrons are in higher energy levels, the atom is in an excitedexcited state and is less stablestable. The atom prefers to be stable, so the electrons fallfall into lower energy levels that are not full. As the electrons fall, energy is releasedreleased in the form of visiblevisible or or invisible invisible lightlight.

atoms prefer…

• to be stable!

• to have low energy!

• to be in their ground state!

Energy within the atom?

Increases away from the nucleus

ENERGY

DEFINE:

energy level AND atomic orbital

AND Read section 5.1 AND answer

questions 1, 2, 4, and 5 on page 132

2 definitions and 4 questions

Day 3 1-3

Radiant AcrosticRADIANT

Day 5 1-5

1. When do we treat light as a wave? As a particle?

2. How did Arthur Compton demonstrate that light can act as a particle?

If a light wave has a frequency (ν) of 3.0 * 1015 Hz, what is its energy?

2.0 * 10-18

m

Review-Style

h

a

Quantum Mechanics

Mr. Bohr was concerned with calculating and predicting the line spectra of elements.

What happens when there is more than 1 electron?

Quantum Mechanics

Mr. Bohr was concerned with calculating and predicting the line spectra of elements. He wondered how electrons move and where they can be found in atoms. Bohr’s ideas worked well for hydrogen with 1 electron. …

What happens when there is more than 1 electron?

Quantum Mechanics

Bohr’s ideas worked well for hydrogen with 1 electron. … He predicted the infrared and ultraviolet bands of hydrogen’s emission spectrum. The equations he used came from Classical Mechanics, a branch of physics that describes the movements and interactions that are large enough to see.

But…Alas.. Bohr could not predict the bright-line spectra.

The laws of Classical Mechanics just don’t cut it for atoms and electrons.

Electrons are tricky… they and other subatomic particles like them have their own code of conduct… They behave differently than anything you may be able to see with your eyes or with any other object. New ideas needed to be looked into, and these new ideas became known as Quantum Mechanics.

Louis de BroglieOne of the first to

think that electrons possess wave wave propertiesproperties. He reasoned that since waves can act as particles do (taken from Planck’sPlanck’s idea about lightlight), then particles might behave as waves do.

For tiny subatomic particles…Wave properties areare importantimportant. As the size of the moving object decreases, its wavelength increasesincreases. The wavelength for a tiny electron can be as large as an entire atomatom.

So how does an electron move in an atom?

Bohr (and maybe you too…) thought that they moved in circularcircular or sphericalspherical orbits.

With de Broglie’s matter-matter-wave ideawave idea, now we theorize that electrons vibrate around the nucleus in a .

Homework # 1