cp5.3--electrons
TRANSCRIPT
Chapter 5: Electrons in Atoms
Section 3:Physics and the Quantum Mechanical Model
Draw and identify the features of a wave; Describe the relationship among the
frequency, wavelength, and energy of light; Identify the general ranges of
electromagnetic radiation and their relative wavelengths and frequencies;
Explain the source of atomic emission spectra;
Explain how the frequencies of emitted light are related to changes in electron energy
Students will be able to…
Light made of electromagnetic waves◦ Considered to be quanta of energy called photons◦ Has properties of particles and waves
I’ve seen the light!
Wavelength (λ) :distance between crests
Amplitude
Frequency (ν): number of wave cycles to pass a given point per unit of time◦ SI unit is Hertz (Hz), or s-1
Two are related by the formula: Since c is constant, λ and ν are inversely
proportional If one is big, the other is small
Light and the Universal Speed Limit
speed of light 3 x 108m/s
If you know either λ or ν, can solve for other Example: What is the wavelength of a
wave with frequency equal to 5.10 x 1014 Hz?
A little light math…
c
cRearrange
The Electromagnetic Spectrum
Energy of light is related to frequency◦ Higher the frequency, more energy
Visible light is small slice in the middle of spectrum◦ Red is lowest ν(longest λ) that the human eye “sees”
The Electromagnetic Spectrum
Ground state: electrons in lowest possible energy level
Excited state: atoms absorb energy and electrons move to higher energy levels ◦ Once energy source is removed, electrons
drop back down to ground state ◦ Emit quanta of energy in the form of… light
(sometimes visible)
So what does this have to do with electrons?
Atomic emission spectrum: pattern of discreet lines given off by electrons dropping to ground state◦ Energy levels are quantized◦ Each line represents a frequency (energy) that is
directly proportional to the energy lost by the electron
◦ No two elements have exactly the same spectrum
Reading between the lines
Each drop an electron makes relates to a specific frequency of energy
Not all is in visible range, but always at discreet frequencies (not continuous)
Reading between the lines
Draw and identify the features of a wave? Describe the relationship among the
frequency, wavelength, and energy of light? Identify the general ranges of
electromagnetic radiation and their relative wavelengths and frequencies?
Explain the source of atomic emission spectra?
Explain how the frequencies of emitted light are related to changes in electron energy?
Objective check: Can you...
Page 140 #14, 15 Page 146 #16, 17, 21
Homework