__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

electromagnetic
(EM) radiation.

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 10^{17}
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 10^{8} 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 10^{8} m/s = λ ^{.} 1.74 x 10^{17} 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 10^{14}
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?