Before Bell Rings Grab 2 Papers From The Side Table Have your Electron Energy and Light Packet out for me to Check

ETD 3 2019 Draw + Explain what is happening when we excite the electrons in an atom.

ETD 3 ANS A 2019 Draw + Explain what is happening when we excite the electrons in an atom.

ETD 3 ANS A 2019 Draw + Explain Bohr’s Experiment and His 5 Big Ideas. Bohr saw that different line spectra were emitted by different elements. These spectral lines are emitted by the electrons as they go from an excited state, which is farther from the nucleus, to the ground state, closer to the nucleus. Since he did not see a full spectrum (rainbow of colors) he was able to determine that electrons can only make certain jumps, from one energy level to another. This lead him think that the electrons orbit the nucleus of the atom, kind of like planets orbiting the sun. He also was able to see that the farther an electron jumped from excited to ground, the more energy it had to release. So if it was a big fall, the wavelength of light emitted would be short and have high energy, like purple. If the fall to closer to the nucleus was small, the wavelength was large and would have low energy, like red.

Get out your notes

Niels Bohr's Experiment

Electron Ladders: Absorption Electrons can only be at specific energy levels, NOT between levels. Excited state We can think of the electrons moving kind of like we move on a ladder. Just like we can’t stop between rungs, the electron can’t stop between energy levels. When an electron gains (absorbs) energy, it moves from its ground state (close to the nucleus) to an excited state (farther from the nucleus). Ground state e- e-

An Excited Electron  Emission Energy Photon of red light emitted When the electron is in the excited state, it needs to release (emit) that energy so it can return to its ground state. The way it does this is through releasing photons. The energy and color of the photon is determined by how far the electron had to fall to get to the ground state. The longer the fall, the more energy it has to release. So longer falls will be towards the violet end of the spectrum and shorter falls towards the red end of the spectrum. Ground energy state Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 326

Color = Energy of Photons Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 329

This is what Bohr finally ended up with This is what Bohr finally ended up with. The protons and neutrons in the center of the atom (nucleus). The electrons were in orbits around the nucleus at different energy levels. As the electrons absorbed energy, they moved farther from the nucleus. As they lost energy in the form of photons, they moved closer to the nucleus.

Bohr Model e- orbits = Energy levels

Element Tubes Use the spectroscope to see the line spectra from different elements On for 30 sec, off for 30 sec Hydrogen at station 3, Ne at 4, Incandescent Blub at 5

H He Ne

Bohr Model of an Atom Not perfect Protons and neutrons in the center Rings of electrons outside 2,8,8,18,18,32,32 rule Happy with a full outer ring, unhappy without

Homework Make sure to turn Super Models Packets on front table Bohr Model, Emission Spectra WS due next class Lab next class, so legs covered and closed toed shoes. Also some way to tie back your hair if it is long.