Aim: How Do We Describe an Atoms Energy Levels?

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Presentation transcript:

Aim: How Do We Describe an Atoms Energy Levels? Describe Picture. What’s involved? Which elements? What does it tell us about each element? Pick an element, color tells us what? Frequency or wavelength tells us what? Energy! Why are there so many??? FIGHT! HW: Study for Quiz

Do Now! Describe two physical attributes of a photon. What does a photon have? 2. What equation is associated with a photon’s energy? 3. A photon has 5 eV of energy. What is this energy in joules? What is that photons wavelength? Energy, momentum

How do electrons play Atomic Frogger!? Energy Level Jumping

Draw your idea of Bohr’s Model of the atom… Atoms have different energy levels. Each level requires a DISCRETE (Specific) amount of energy.

Hydrogen Absorption Spectrum When light is incident on a hydrogen atom, it can absorb the photons with the correct amount of energy that allow the electrons in the atom to ‘jump’ to their excited states. An absorption spectrum is the rainbow of colors with the colors matching the correct energy jumps missing.

Hydrogen Emission Spectrum Once an electron has reached the excited state by absorbing the correct amount of energy. The electron will stay there for a moment then return back down to the ground state. When the electron falls back to the ground state, it emits a photon with an energy equal to the energy difference between the level it came from and the level it went to.

Hydrogen Emission Spectrum Pick a different color than before. Determine a possible frequency of that color using the Reference Tables. Calculate the energy a photon of that color Convert that photon’s energy into eVs. Using your Reference Tables decide which energy level transition could be caused by that photon.

Why don’t we see a color for every transition on emission spectrum? Other transitions result in frequencies that correspond to ultraviolet or infrared. Balmer Series: Visible spectrum of light from a hydrogen atom. Results from photon emissions when electrons jump down to n=2

Energy Levels What does it mean if a photon is absorbed? An electron gains energy and is excited. How about if a photon is emitted? Electron falls to a lower energy level.

Trick Questions To what level can an 11 eV photon excite an electron? NONE! Energy levels are specific! How about a 14 eV photon? The electron is ejected entirely with KE= 14eV-13.6eV

Ionization Energy The energy required to remove an electron from an atom. Determine the minimum energy required to ionize a hydrogen atom in the n=4 state.

What are possible transitions? Possible transitions include an electron jumping or falling to a new energy level. How many are there for hydrogen between n=1 and n=3? 6 possible!!! Transitions include from 2 to 3 and 3 to 2, not just 1 to other levels.

Summary How does an electron become excited? Describe ionization energy. When is a photon emitted? What is the equation for momentum of a photon? How do electrons behave?