Flame Spectroscopy Lab
Red: Longer WavelengthPurple: Shorter Wavelength The wavelength is the inverse of the frequency of the emitted light Bohr Model & Color Spectroscopy An electron can transition between energy levels by absorbing energy to jump to a higher level (excited state), and then emitting light photons of a particular color when it relaxes to the normal level (ground state) 1. Absorb energy 2. Emit energy as a light photon
Spectroscopy: Element Identification and Emission Spectra The energy levels in atoms and ions are the key to the production and detection of light. Energy levels or "shells"exist for electrons in atoms and molecules. The colors of dyes and other compounds results from electron jumps between these shells or levels. The colors of fireworks result from jumps of electrons from one shell to another. Observations of light emitted by the elements is also evidence for the existence of shells, subshsells and energy levels. The kinds of light that interact with atoms indicate the energy differences between shells and energy levels in the quantum theory model of the atom. Typically the valence electrons are the ones involved in these jumps. The "quantum" theory was proposed more than 90 years ago, and has been confirmed by thousands of experiments. Science and education has failed to clearly describe the energy level concept to almost four generations of citizens. This experiment is an exercise aimed at throwing a little more light on the subject. ( Don't laugh too hard at the joke.) Atoms have two kinds of states; a ground state and an excited state. The ground state is the state in which the electrons in the atom are in their lowest energy levels possible (atoms naturally are in the ground state). This means the electrons have the lowest possible values for "n" the principal quantum number. Specific quantized amounts of energy are needed to excite an electron in an atom and produce an excited state. The animation shows the opposite of excitation. It shows how the excited hydrogen atom with an electron in the n = 3 shell can release energy. If the electron in hydrogen only drops to the n = 2 shell the energy matches a pulse of red light.
Wavelength Wavelength is the distance between the beginning and end of a complete cycle of the light wave. Each color has a characteristic wavelength. All colors of light travel at the same speed, 3.0 x 10 8 meters/ second. Longer Wavelength Shorter Wavelength
Flame Spectroscopy Lab Safety Wear goggles at ALL times Don’t Touch the flame or knock over the burner: it’s hot! Don’t Touch the chemicals: wash with soap and water immediately if you touch anything accidentally – CuCl 2 is highly toxic by ingestion; avoid contact with eyes, skin and mucous membranes. – LiCl is moderately toxic by ingestion; avoid contact with eyes, skin and mucous membranes. Wash Table and Hands at end of lab
Data Table Name of Metal Atomic Symbol Color of Solution Color of Flame Lithium Strontium Sodium Copper Potassium UNKNOWN
Sample Tray Layout ? Cu Li K Sr Small Trays Large Trays Na
Notes Person 1Person 2Person 3 Wear GogglesGet sample tray & cork/needle. DO NOT SPILL ANY! Get beaker & fill w/100ml water Wet the wet rag in the sink, wring dry. Do not touch or inhale or eat any chemicals Wash & rinse cork/needle in sink Record sample elements and liquid color Light burner Do not spill any chemicals – if you do, wipe it up with a wet paper towel Clean needle in flame for 15 sec If the burner flame goes crazy, put the wet rag over it, & tell Mr. Rosato Dip needle in chemical for 15 sec Testing the SolutionsPlace needle in flame Record flame colors at beginning & end rinse needle in beaker. Clean needle in flame for 15 sec Repeat for each chemical but switch roles CLEAN UP Return all supplies where you got them wipe the table with a wet paper towel EVERYBODY WASH YOUR HANDS IN THE SINK WITH SOAP!
Light/Color Emission plets/Bohr/frame.html plets/Bohr/frame.html on-flame-exp.html on-flame-exp.html
Sample Tray Key Li Cu Li K Sr Red Pink/Red Red Purple Red Small Trays Are empty Large Trays Sr