Download Electrons in Atoms Section 5.1

Section 5.1 Continued
Particle Nature of Light
Objectives
• Compare the wave and particle models of
light.
• Define a quantum of energy and explain
how it is related to an energy change of
matter.
• Contrast continuous electromagnetic
spectra and atomic emission spectra.
Particle Nature of Light
• Besides having wave characteristics, light also
acts like a particle.
• The Quantum Concept: Energy can only be
gained or lost in a specified amount  A
Quantum.
• Equantum = hv
• h is Plank’s Constant = 6.626 x 10-34 J•s
Blocks and Quanta
• Think of energy transfer like building a
wall of Legos®.
• I can only add or take away 1 Lego.
• There is no such thing as a ½ Lego.
Particle Nature of Light
• Photoelectric Effect: electrons, called
photoelectrons, are emitted from a metal’s
surface when light of a certain frequency
shines on the surface.
Photoelectrons
Light
The Photon
• Photon:
– particle of electromagnetic radiation
– no mass
– carries a quantum of energy
• Ephoton = hv
Neon Signs
Atomic Emission Spectra
• Electricity passed through a tube of gas
• Gas atoms absorb energy and become excited
• Atoms release the energy absorbed in the form
of light.
• Each atom has specific frequencies it will
release in the light form.
Atomic Emission Spectra
Hydrogen (H)
Helium (He)
Oxygen (O)
http://astro.u-strasbg.fr/~koppen/discharge/index.html
Atomic Emission Spectra
Neon (Ne)
Xenon (Xe)
http://astro.u-strasbg.fr/~koppen/discharge/index.html
Homework
• 7-12 on page 126