Lab Report for Experiment #7
Student's Name __________Lisa __________
Date of Experiment _08/03/2013__________
Date Report Submitted ______08/05/2013___________
Identification of Metallic Ions
Purpose: To perform and observe the flame tests of some alkali and alkaline earth metal ions.
Electrons from an atom can absorb energy and become excited to move from the stable “ground state” energy level to a higher energy level. Imagine one of the electrons “jumping” from the second energy level to the unoccupied 6th energy level, then “relaxing” back to the 5th energy level. As these electrons relax and go back from the higher energy level to the lower energy level, energy is released as visible light. This is the result of photons emitted (released) as electron energy is lowered. Photons are thought to behave as waves. For ocean waves the distance form wave tip to wave tip can be measured, this distance is called the wavelength. Waves with a large amount of energy have a shorter wavelength, and waves with lower energy have longer wavelengths. Similarly, high energy photons have short wavelengths, which for light in the visible range, is the purple end of the spectrum, about 400nm. Conversely light in the red region has a wavelength of 650nm and has a lower energy.
As you have seen in the modules, each atom has a unique arrangement of electrons and scientists take advantage of this concept to identify materials based on the colors that are emitted. This can be done using scientific instruments called spectroscopes by comparing samples of pure elements with unknown substances. In this lab you will be observing the colors of light emitted when samples of known metallic ions are exposed to flame, thus absorbing energy, and carefully observing the color change in the flame. You will also have an unknown sample that is one of the “knowns”. The unknown can be identified by comparison to...
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