Review section 5.3 AND complete #s 19, 20, 22, and 23

on page 148

1. How can electrons move from one energy level to another? They must…

Day 1 12-13

Energy Source

Absorbed EnergyEnergy Released

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

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.

Spectroscopes

Day 2 12-14

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

2. How did Arthur Compton demonstrate that light can act as a particle? notes page 3

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.

Large moving objects

Wavelengths are small and practically unnoticed.

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 .

The Elusive Electron Evades Subatomic State Trooper!

Werner HeisenbergIn 1927, he

proposed the Uncertainty Uncertainty PrinciplePrincipleThis states that it is

impossible to know both the speedspeed and locationlocation of an electron at the same time.

Why is it so hard to pinpoint the electron?

To determine the speed and the location of an object, you must be able to SEE the object… light is bounced off the object when you see it.

Light is made up of quanta or photons.

When photons hit a speeding car, the car is unaffected. But when a photon hits a speeding electron, the electron will move or change direction. So, if a photon hits an electron and the light bounces off it into your eyes, you will see where the electron was, but you won’t know how fast it was going at the time.

Heisenberg

Explain the Heisenberg Uncertainty Principle.It is impossible to know both the speedspeed and locationlocation of an electron at the same time.

What, am I speeding?

Assignment