Atomic Emission Spectra. Drill – 11/9 Read the Emissions Spectroscopy Intro!
-
Upload
fay-wilkinson -
Category
Documents
-
view
222 -
download
5
Transcript of Atomic Emission Spectra. Drill – 11/9 Read the Emissions Spectroscopy Intro!
Atomic Emission Spectra
Drill – 11/9
Read the Emissions Spectroscopy Intro!
Drill – 11/09
1. Draw a wave and label it with wavelength and amplitude.
When finished, read the Emissions Spectroscopy Intro!
Drill – 11/10
1. What happens during electron absorption?
2. What happens during electron emissions?
How is Light Energy related to Color?
White light is made up of all colors of the spectrum
When passed through a prism a continuous spectrum (rainbow effect) is obtained
Elements Emit only Specific Wavelengths
Individual elements emit a spectrum containing discrete lines
This is called a line spectrum
Electrons Surround the Nucleus
Electrons surround the nucleus and travel at the speed of light
They are found in only certain allowed energy levels or orbitals
Electrons are at the lowest energy level – the ground state.
Different Energy States are Possible
When the electrons in an atom become excited by absorbing energy from the surroundings, they jump to new higher energy levels.
The excited state is less stable than the lower energy state therefore the electron falls back or returns to the lower energy ground state.
Return to Ground State
When electrons fall back a wave with a specific amount of energy is emitted – called a photon. If we see color then the emission is in the visible range
We perceive this as unique colors associated with particular elements
Bright Line Emission SpectrumElement X
shorter wavelength longer wavelengthhigher frequency lower frequencyhigher energy lower energy
Each line corresponds to the energy emission when an e- falls from excited to ground state
Lines converge at higher energy indicating a smaller energy difference between levels further away
Data from Line Spectra …
#1. Electrons exist in distinct energy levels
Each line represents the energy emitted as an electron falls from excited to ground state
Data from Line Spectra
#2. Energy differences are smaller between levels that are further from the nucleus
Lines are closer together on the higher energy end of the spectrum
Electromagnetic Spectrum
10-12 10-9 10-6 10-3 1 103 (m)
V I B G Y O R
Visible light
Gamma X-ray UV IR Micro Radio
Electromagnetic Radiation is energy in Waves
The length of the wave is inversely related to its frequency
c = λνSpeed of light = wavelength × frequency
(m/s) (m) (1/s)
Speed of light = 3.00 × 108 m/s
Frequency is a measure of waves/second and has the units of 1/s or Hertz (Hz), the SI Unit.
Electromagnetic Radiation is energy in Waves
The frequency of the wave is directly related to its energy
E = hvEnergy = (Planck’s Constant) (frequency)
(J) (J • s) (1/s)
Planck’s Constant = 6.626x10-34 J • s
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/linesp16.swf
Determine the frequency of light whose wavelength is 4.257x10-7cm