CHEM 1A Lecture Notes - Lecture 36: Gas-Filled Tube, Electron Excitation, Photon Energy

44 views4 pages

goldhound747

6 Apr 2016

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Individual atoms interact with electromagneic radiaion in two diferent ways depending on whether the energy of the light is greater than or less than the ionizaion energy. Absorpion of light with energy greater than the ionizaion energy is coninuous or non-- quanized. All energies of light are absorbed resuling in ejecion of an electron. Photon energy in excess of the ionizaion energy is channeled into the kineic energy of the ejected electron. Absorpion of light with energy less than the ionizaion energy is discrete. It is possible only when the energy of an incident photon equals the energy required to promote an electron from the ground state to an excited state. If the photon energy does not match that sharply deined energy diference between the two orbital energies, the light cannot be absorbed and is therefore transmited. It must be absorbed in its enirety or not at all. Electrons in atoms can only have speciic, quanized energies.

Related Questions

1- An electron in the 8^th energy level of the H atom drops to the 2^th energy level. In other words an electron in an excited state drops to a less excited state. What is the energy (in J) of the emitted photon? The energy of an electron in the nth level is

2-The absorption spectra of ions have been used to identify the presence of the elements in the atmospheres of the sun and other stars. What is the energy of a photon (in J) that is absorbed by He⁺ ions, when an electron is excited from the Bohr orbit with n = 2 to the n = 6 state? The energy of an electron in the nth level is

3e) If an electron in the ground state of hydrogen absorbed a photon of light that has an energy of 1000 kJ, will the electron make an energy transition? Explain why or why not.

3f) Identify the energy of a photon in kJ that would result in the transition of an electron from the ground state to the n=5 energy level?

3g) If an electron makes a transition from any energy level nÂ³3 and drops to the energy level n=2, identify its hydrogen emission series and its electromagnetic range.

Hydrogen Emission Series Name	Electromagnetic Range Name

3h) Why are the Lyman and Paschen Series in the hydrogen emission spectrum not observable with visual senses or the spectroscope?

3i) Why does it appear that there is a continuous band of color in the emission spectrum of multi-electron atoms such as mercury.

Use a ruler to calibrate the spectral limits in the figure above. In other words, what are the right and left limits in nm, and what is the equation that converts distance on this page in cm to spectral units of nm? This âcalibrationâ will help you with the next item.

Use the NIST Atomic Spectral Database to assign the three bright spectral lines in the hydrogen spectrum.

Abstract This physical chemistry laboratory exercise will have students work with provided emission spectra for several elements and data collected on the NIST Atomic Spectral Database. First, students will develop a method for calculating what wavelengths of visible light are associated with the most intense spectral lines in the provided visible emission spectra. Then, the NIST Atomic Spectral Database will be accessed in order to identify select properties associated with the four most intense spectral lines. Introduction The emission process can be described in two general parts. Initially, energy is absorbed by an atom, and its electrons can be moved into higher energy (excited) states from their ground state The excitedrelectrons then "relax" and drop back to their ground state. Energy lost during an electron's retaxation process is emitted as a photon. Recall that the energy of a photon is photon upper E lower Where Ephoton is the energy of the photon that is emitted when the emitter drops from an upper energy state to a lower energy state, h is Planck's constant, c is the speed of light, and v is the wavenumber. Remember that the length units should match for c and v This is a good time to revisit a few concepts. Atoms and molecules possess discrete energy levels their energy levels are quantized and not continuous. Using eq 7.1, it is possible to determine the energy associated with a specific excited state to ground state transition if we can determine the wavelength of emitted light. Also keep in mind that there are selection rules that limit the type of transitions we can expect to observe. All of these points are reflected in an elemental or ionic emission spectrum. The visible light spectrum falls within a fairly narrow range of wavelengths, from approximately 400 to 700 nm. Even so, discrete spectral lines are seen in each element's visible light emission spectrum. Each (take some time to reflect on why that would be), each element also has a unique emission spectrum. This provides a diagnostic tool for determining the composition of a sample. As an example, the elements present in celestial objects can be determined by the light that they produce line represents one possible transition. Since each element has unique energy levels Some of the transitions observed in this lab exercise involve d-orbitals. As such, a discussion regarding d-orbitals and related selection rules is necessary at this point. The first goal is to determine which character table should be used. Start by observing the shape and relative orientations of the d-orbitals. Refer to Figure 1 below

CHEM 1A Lecture Notes - Lecture 36: Gas-Filled Tube, Electron Excitation, Photon Energy

Document Summary

Get access

Related textbook solutions

Chemistry: Structure and Properties

Basic Chemistry

Principles of Chemistry Molecular Approach

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related Documents

CHEM 1A Lecture Notes - Lecture 5: Photoemission Spectroscopy, Phototube, Photocathode

CHEM 1A Chapter 2: Atoms and Quantum Theory

CHEM 1A Lecture Notes - Lecture 35: Atomic Emission Spectroscopy, Absorption Spectroscopy, Black-Body Radiation

Related Questions