ATOMIC SPECTRA AND THE BOHR MODEL OF THE ATOM
Atomic Structure Activity: The Electromagetic Spectrum and Atomic Spectra
1. a) What is the electromagnetic spectrum?
The full array of all types of ______________ ______________ is called the electromagnetic spectrum. It extends
from the shortest wavelength _____________ rays to the longest wavelength __________waves. *Visible light forms only
a _______ portion of the full electromagnetic spectrum. In a vacuum, all EMR travels at the speed of _________
(______________m/s)
b) What distinguishes one type of EMR from another?
 ______________/______________
 Wavelength and frequency are _______________ related – as the frequency of the EMR increases, the wavelength
______________ and vice versa.
2. How is the energy of a photon calculated?
E = _____
Where:
E is the energy in _____________ (J)
h is ___________ ____________ (6.6 x 10-34)
f is the _________________ (of the EMR) in hertz (Hz)
Example:
Ultraviolet (UV) light that causes tanning and burning of the skin has a higher energy per photon than infrared (IR) light
from a heat lamp.
*Calculate the energy of a 1.5 x 1015 Hz UV photon and a 3.3. x 1014 Hz IR photon.
 energy of UV photon:
energy of IR photon:
E = hf
E = hf
=
=
=
=
*Therefore, the energy of a photon is solely dependant on the _________________ of the EMR.
(i.e. higher frequency = more ______________)
(e.g. E of UV photon > E of blue light photon > E of red light photon > E of infrared photon etc.)
3. a) What is a spectroscope?
 invented by Robert Bunsen and Gustav Kirchoff
 Their spectroscope was a _________ that split light into its component frequencies. [e.g. A spectroscope splits white
light into a __________________ (colours blend into one another) “rainbow” spectrum.
Remember: Each colour represents a different frequency/wavelength of EMR.
b) What is spectroscopy?
 a technique for analyzing atomic ________________ (e.g. Stellar spectroscopy is a technique used to identify the
_______ present in the atmospheres of distant stars.)
4. What is an emission (____________-line) spectrum? How is it attained? (**ACTIVITY  gas discharge tubes)
 When a gas is excited by __________ or ______________, for example, and then passed through a
__________________, a series of bright lines (against a ___________ background) of light are produced. The resulting
array of bright lines is called an ___________________spectrum.
 A bright-line spectrum is not _____________________ (i.e. a complete rainbow of colours is not observed).
*View the following ANIMATION: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/linesp16.swf
5. What is an absorption spectrum (____________-line spectrum)? How is it attained?
*Absorption Spectra: http://jersey.uoregon.edu/vlab/elements/Elements.html
 A cool gas in front of a continuous source of light produces an ________________ spectrum – a series of dark
spectral lines (i.e. missing parts) among the colours of the rainbow.
 This is the type of spectrum observed in stellar (star) spectroscopy.
6. What is the relationship between the bright and dark-line spectrums of an element?
 The dark lines in an element’s absorption spectrum are in the _________ position as the bright lines in the emission
spectrum of the same element.
7. How do the emission/absorption spectrums produced by different atoms compare?
 Each element produces its own ___________ emission/absorption spectrum. The emission/absorption spectrum of an
element can be thought of as its “______________”. This is why stellar spectroscopy is so powerful.
 (e.g. Although we are unable to travel to distant stars/galaxies, we are able to analyze the light emitted by these objects
– the light that hits our telescopes and spectroscopes, that is. The light emitted by our sun produces a spectrum consistent
with the “fingerprint” of helium. (“helios” = Greek word for “sun”) *Interestingly, helium was “discovered” on the sun
before it was discovered here on Earth.
Specific Example: THE EMISSION SPECTRUM OF HYDROGEN
*ANIMATION: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/linesp16.swf
*ground state = the _____________ energy state available to an electron (also – state of greatest stability)
*excited state = any level _____________the ground state
*When an electron moves from the ground state to an excited state, it must ___________ energy. When it moves from an
excited state to the ground state, it ___________energy. This release of energy is the basis for ___________
___________.
Example:
*When an electron of a hydrogen atom has been excited (in an electrical gas discharge tube, for example) to the third
energy level falls to the second energy level, it ________ light with a specific energy. This energy corresponds with a
specific wavelength in the electromagnetic spectrum. Specifically, an electron that makes a transition form the 3 rd energy
level to the 2nd energy level emits exactly 3.03 x 10-19 joules of energy which corresponds with a photon of ________ light
with a wavelength of _____ nm (___ x 10-7 m).
λ=
hc
E
*Where h is Planck’s constant (6.6 x 10-34) and c = the speed of light (3.0 x 108 m/s).
=
=
Hydrogen’s Emission Spectrum:
 The photon of green light = electron transition from level ____ to 2.
 The photon of blue light = electron transition from level ____ to 2
 The photon of violet light = electron transition from level ____ to 2.
**Notice that all of these transitions are from a _________ level down to level 2. Transitions down
to energy level 2 are referred to as the ____________ series. Are other transitions possible?
*The ___________ series = transitions from higher levels down to level 1
 These transitions result in the emission of EMR in the _________________ portion of the
spectrum. Therefore, the “lines” produced by these transitions ____________ be seen with the
naked eye.
*The ______________ series = transitions from higher levels down to level 3
 These transitions result in the emission of EMR in the ____________ portion of the spectrum.
Therefore, these “lines” cannot be seen with the naked eye either.
*Electrons dropping back to the lowest energy level (n=1) emit the ______ energy.
SUMMARY:
**What’s important to remember is that the emission spectrums produced by “excited” atoms extend into ranges of the
EMR spectrum that we cannot ___________. As a result, the portion of the emission spectrum that we tend to focus on is
the one we can see with the unaided eye.
*Line Spectra(Interactive):
http://www.rsc.org/Education/Teachers/Resources/Databook/int_electron_energy_hydrogen.htm