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

Energy Source Absorbed Energy Energy Released

Ground vs. Excited States: ground closest stable An atom is in the ground state when its electrons fill the lowest possible energy levels that are closest to the nucleus. This is when the atom is most stable. gain jump exact amount An electron can gain energy and jump to a higher energy level. The electron must absorb an exact amount …

gain jump exact amount photon An electron can gain energy and jump to a higher energy level. The electron must absorb an exact amount … of energy to make a jump to a specific energy level. The energy that the electron gains comes from a photon. Ground vs. Excited States:

excited stable When an atom’s electrons are in higher energy levels, the atom is in an excited state and is less stable. fall released visibleor invisible light The atom prefers to be stable, so the electrons fall into lower energy levels that are not full. As the electrons fall, energy is released in the form of visible or invisible light.

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 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 Broglie wave properties Planck’slight One of the first to think that electrons possess wave properties. He reasoned that since waves can act as particles do (taken from Planck’s idea about light), then particles might behave as waves do.

Large moving objects Wavelengths are small and practically unnoticed.

For tiny subatomic particles… are important increases atom Wave properties are important. As the size of the moving object decreases, its wavelength increases. The wavelength for a tiny electron can be as large as an entire atom.

So how does an electron move in an atom? circularspherical Bohr (and maybe you too…) thought that they moved in circular or spherical orbits. matter-wave idea With de Broglie’s matter-wave idea, now we theorize that electrons vibrate around the nucleus in a.

The Elusive Electron Evades Subatomic State Trooper! Werner Heisenberg Uncertainty Principle In 1927, he proposed the Uncertainty Principle speedlocation This states that it is impossible to know both the speed and location 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. speedlocation It is impossible to know both the speed and location of an electron at the same time. What, am I speeding?

Assignment