Transcript PHYSICS & THE QUANTUM MECHANICAL MODEL

Chapter 5 – Electrons in Atoms
text pages 134-171
HISTORY
• Isaac Newton thought of light as consisting
of particles (1700’s)
• By the 1900’s most scientists believed light
was a form of waves
• The wave model describes light consisting
of electromagnetic waves
Review of Waves
ELECTROMAGNETIC RADIATION
• Series of waves including the visible &
invisible
• Travels in a vacuum at 3.0 x 1010 cm/s or
3.0 x 108 m/s
The electromagnetic spectrum
FREQUENCY DECREASING & WAVELENGTH INCR
FREQUENCY vs. WAVELENGTH
Wavelength (λ) -- distance between two crests
Frequency (v) -- number of waves to pass a point per unit time
Speed of light (c) – constant, 3 x 108 m/s
Frequency and wavelength have an inverse relationship
c= λ v
Calculate the wavelength of the yellow light emitted
by a sodium lamp if the frequency of the radiation is
5.10 x 1014 s-1.
c= λ v
v= 5.10 x 1014 s-1
c= 3.0 x 108 m/s
λ=?
Who is Max Planck?
studied visible emissions from hot glowing solids
proposed that light was emitted in “packets” of
energy called quanta (a.k.a. photons)
the energy of each packet was proportional to the
frequency of the light wave
According to Einstein and Planck, the energy
of a quantum, E = h x v
Planck’s constant (h)=6.6262 x 10-34 J x s
Calculate the energy of a photon whose
frequency is 3.55 x 1015 s-1.
E=hxv
v = 3.55 x 1015 s-1
h = 6.6262 x 10-34 J x s
The photoelectric effect is when electrons are emitted from a
metal’s surface when light of a certain frequency shines on it.
Alkali metals are particularly subject to the effect