Atomic Emission Spectra

Drill – 11/9 Read the Emissions Spectroscopy Intro!

Drill – 11/09 Draw a wave and label it with wavelength and amplitude. When finished, read the Emissions Spectroscopy Intro!

Drill – 11/10 What happens during electron absorption? 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 Spectrum Element X shorter wavelength longer wavelength higher frequency lower frequency higher energy lower energy Lines converge at higher energy indicating a smaller energy difference between levels further away Each line corresponds to the energy emission when an e- falls from excited to ground state

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 V I B G Y O R Visible light Gamma X-ray UV IR Micro Radio 10-12 10-9 10-6 10-3 1 103 (m)

Electromagnetic Radiation is energy in Waves The length of the wave is inversely related to its frequency c = λν Speed 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 = hv Energy = (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