Electrons, Energy, & the Electromagnetic Spectrum

Simplified, 2-D Bohr Model: Orbits, paths, shells, rings = ENERGY LEVELS

As the name “energy level” implies, there is a
specific amount of energy associated with each
energy level.

Electrons are lazy – they will occupy the
location that requires the least amount of
energy

Lowest energy state = GROUND STATE

For hydrogen in the ground state…  ~ Electron is located in energy level 1                                                                                                                                                         (E 1) because E1 is closest to the
nucleus.  Nucleus is positively-charged                                                                                                                                                                  & attracts negatively-charged e-.                                                                                                                                                              Therefore, low amount of energy                                                                                                                              Nucleus              needed to be in E1. Electron

If energy (from an outside source) is added to the atom…  Electron jumps to a higher energy level because
energy is absorbed.  (Electron is now in the
EXCITED STATE.) Add energy                                                                   As soon as the electron jumps to a higher level,
it immediately falls back to a lower energy level.
When the electron falls, energy is released.
energy
released                                                                        The energy is released in the form of

The type or form of EM radiation released
depends on the difference in energy between
the energy levels.

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Here’s how the type/form of EM radiation can be determined…

The amount of energy released when an electron falls from a higher to a lower energy level is directly proportional to its frequency.  The calculation follows the equation:             E = h . ν

E = Energy (unit is J)
h = Planck’s Constant (6.626 x 10-34 J.s)
ν  = frequency (unit is Hz or 1/second)

EXAMPLE 1:  A particle of EM radiation has an energy of 1.15 x 10-16 J.  What is its frequency?
1.15 x 10-16 J = 6.626 x 10-34 J.s . ν
ν = 1.74 x 1017 Hz

The type of electromagnetic radiation can be determined if one knows the wavelength.  The wavelength is inversely proportional to the frequency.  The calculation follows the equation:      c = λ . ν

c = speed of light (3.00 x 108 m/s)
λ  = wavelength (unit is m)
ν  = frequency (unit is Hz or 1/s)

EXAMPLE 2:  What is the wavelength of the same particle from EXAMPLE 1?
3.00 x 108 m/s = λ . 1.74 x 1017 Hz
λ = 1.72 x 10-9 m

EXAMPLE 3:  What type of electromagnetic radiation is the particle from EXAMPLE 1?
answer for wavelength is 10-9  so use chart below to determine…
x-rays or ultraviolet (either one is acceptable) PROBLEMS FOR YOU TO TRY ON YOUR OWN…

1.) A particle of EM radiation has a frequency of 5.76 x 1014 Hz.
(A) How much energy does this particle have?
(B) What is the wavelength of this particle?
(C) What specific type of electromagnetic radiation does this particle represent?

2.) A particle of electromagnetic radiation has 2.39 x 10-13 Joules of energy.
(A) What is the wavelength of this particle?
(B) What type of electromagnetic radiation does this particle represent?