Atomic Spectra &
The Periodic Properties Of Elements
Objectives
1. Determine the emission spectrum of Hydrogen and other elements.
2. Calculate the expected wavelengths of H using the Rydberg equation.
3. Discover the relationship between the chemical reactivity of various
elements and their positions on the periodic table.
Animation of the
dispersion of white
light as it travels
through a triangular
prism.
History of Optics & Light Studies
Ibn Alhazen is considered the
“Father of Optics” He wrote the
“Book of Optics”, which correctly
explained and proved the modern
theory of vision. His experiments
on optics greatly influenced later
scientists.
His experiments included ones
on lenses, mirrors, refraction,
reflection, and the dispersion of
light into its constituent colors. He
studied the electromagnetic aspects
of light, and argued that rays of
light are streams of energy particles
traveling in straight lines.
Ibn Alhazen
(965 – 1039)
Arab Muslim Scientist
“Father of Optics”
Historical Background of Spectroscopy
In 1608, Galileo Galilei is credited as
the first to turn his telescope to the
heavens.
He soon discovered craters on our
Moon, sun spots, the moons of Jupiter,
and that Venus has phases like our
Moon.
Galileo claimed that his observations
only made sense if all the planets
revolved around the Sun (as proposed
by Aristarchus and Copernicus) rather
than the Earth.
The Inquisition eventually forced Galileo
to publicly recant this conclusion.
Galileo Galilei
1564 - 1642
A Quantitative Study of Light
Sir Isaac Newton was one of the
first people to study light
scientifically.
In 1672, Newton directed a beam
of white light through a triangular
bar of glass, called a “prism”. He
discovered that the light coming
out of the prism was separated into
bands of colors.
The arrangement of colors
produced by a prism is called a
“spectrum”.
Sir Isaac Newton
1643 - 1727
Prior to this it was believed that
“white light” was equal to purity.
Original Studies Of Light Used Only One Prism
.
When a narrow band of light from a “white” light source is
sent through a prism, a continuous spectrum containing all
wavelengths of visible light is formed.
Newton’s Contribution to Spectroscopy
Newton contributed more to spectroscopy than scientifically
proving that sunlight traveling through a prism was always
broken down into the components of the rainbow.
In fact, his main contribution was to show that after the sunlight
had been broken down into its components by one prism, if a
narrow ray of the light from the first prism was passed through
another prism no further breakdown of light occurred.
Classification of Electromagnetic Radiation
The color components of light are separated along the visible
range of light. The visible range of light (400-700 nm) is
merely a small portion of the entire electromagnetic spectrum.
Advancements in the Study of Light
Joseph von Fraunhofer discovered the dark
absorption lines in the Sun's spectrum (known
as Fraunhofer lines) and designed achromatic
telescope objectives.
At age 11, he was orphaned and forced to
apprentice for no pay with a harsh glassmaker
named Philipp Anton Weichelsberger. In 1801,
the glass shop collapsed and Fraunhofer was
buried alive.
Joseph von Fraunhofer
(March 6, 1787 – June 7, 1826)
German Optician
When Fraunhofer survived the collapse, the
court-councilor von Utzschneider, gave him
books on mathematics and optics. King Max
Joseph gave him a present of eighteen ducats.
With this money Joseph acquired his own glass
grinding machine and bought his release from
Weichelsberger.
Development of the Spectroscope
Joseph von Fraunhofer’s initial desire was
to create a glass lens that did not produce an
image that was fringed with a rainbow of
colors. He realized the problem was that the
glass lens bent some colors more than
others. He began searching for a source of
light of a single color.
Joseph von Fraunhofer
(March 6, 1787 – June 7, 1826)
In 1814, he developed a spectroscope to
study the spectrum of the light given off by
the sun. He was amazed to discover that in
the midst of the rainbow of colors was a
series of black lines.
These dark lines were later determined to be
the result of the absorption of selected
frequencies of the electromagnetic radiation
by an atom or a molecule.
Fraunhofer lines observable in the Solar Spectrum
390 nm
700 nm
Development of Diffraction Gratings
Fraunhofer also completed an important theoretical work on diffraction
and established the laws of diffraction. One important innovation that
Fraunhofer made was to place a diffraction slit in front of the objective of a
measuring telescope in order to study the solar spectrum. He later made and
used diffraction gratings with up to 10,000 parallel lines per inch. By means
of these gratings he was able to measure the minute wavelengths of the
different colors of light. (Diffraction gratings will be discussed more later.)
1855-1860 - Gustav Kirchhoff and Robert Bunsen
Gustav Robert Kirchhoff
Robert Wilhelm Eberhard Bunsen
(March 12, 1824 – October 17, 1887)
German Physicist
(March 31, 1811 – August 16,1899)
German Chemist
Bunsen and Kirchhoff further developed the spectroscope by
incorporating the Bunsen burner as a source to heat the elements. In
1861, experiments by Kirchhoff and Bunsen demonstrated that each
element, when heated to incandescence, gave off a characteristic color of
light. When the light was separated into its constituent wavelengths by a
prism, each element displayed a unique pattern or emission spectrum.
Emission Spectra Complement Absorption Spectra
The emission spectrum seemed to be the complement to the mysterious
dark lines (Fraunhofer lines) in the sun's spectrum. This meant that it
was now possible to identify the chemical composition of distant objects
like the sun and other stars. They concluded that the Fraunhofer lines in
the solar spectrum were due to the absorption of light by the atoms of
various elements in the sun's atmosphere.
Hydrogen Spectrum – The Balmer Series
In 1885, Johann Jakob Balmer
analyzed the hydrogen spectrum and
found that hydrogen emitted four
bands of light within the visible
spectrum. His empirical formula for
the visible spectral lines of the
hydrogen atom was later found to be a
special case of the Rydberg formula,
devised by Johannes Rydberg.
Johann Jakob Balmer
(May 1, 1825 – March 12, 1898)
Swiss Mathematician &
Honorary Physicist
Wavelength (nm)
Color
656.2
red
486.1
blue
434.0
blue-violet
410.1
violet
Quantum Properties of Light
E = nh
E – the change
in Energy
n= 1, 2, 3, …
h – (Planck’s
constant)
h = 6.62610-34 Js
Max Karl Ernst Ludwig Planck
 = frequency
(April 23, 1858 – October 4, 1947)
German Physicist
The Nobel Prize in Physics 1918 for
The discovery of energy quanta.
The profile of radiation
emitted from a black body
In 1900, Planck hypothesized that energy was quantized (i.e. energy can be
gained or lost only in whole-number multiples of the quantity h.) This hypothesis
was later extended by Albert Einstein to include light. Einstein envisioned light
as small discrete particles of energy which he called photons.
Calculating the Balmer & Lyman Series
The four bands of light
calculated by Balmer can
be simply calculated using
the Rydberg equation:
1
1 *
  R( 2  2 )
n1 n2
Where v = frequency
n = the quantum number
R = (Rydberg constant)
R = 3.29 1015 Hz
1 Hz = 1 s-1
The permitted energy levels of a hydrogen atom.
*This equation will be used on page 159.
Recall that Frequency and Wavelength are related where
frequency times wavelength equals the speed of light.
Wavelength (): Distance between
two consecutive peaks [unit: nm]
Frequency (): Number of waves
per second that pass a given point in
space [unit: s-1 (Hertz)]
 = c
Where C is the speed of light
&
C = 2.9979108 m/s
Since the speed of light is a constant, as wavelength decreases,
then frequency must increase.
 In 1913, Bohr developed a quantum model
for the hydrogen atom.
 Proposed the Solar System model of the atom
where the electron in a hydrogen atom
moves around the nucleus only in certain
allowed circular orbits.
Niels Henrik David Bohr
Oct. 7, 1885 – Nov. 18, 1962
Danish Physicist
The Nobel Prize in Physics 1922
for the investigation of the structure
of atoms and of the radiation
emanating from them.
https://www.youtube.com/watch?v=-YYBCNQnYNM
These orbits then correspond to the energy
levels seen in the Balmer series. (p 167)
Atomic Spectra Experiment
PART A: Hydrogen emission spectrum.
PART B: Emission spectrum of other elements.
PART C: Tests on elements: Mg, Al, Si, Ca & Zn.
PART A: Record Hydrogen line spectrum
with a Scanning Spectrophotometer.
The hydrogen line spectrum contains only a few discrete wavelengths.
In the visible region, there are only four wavelengths.
Scanning Spectrophotometer (top view)
A hydrogen light source will be viewed using a scanning spectrophotometer.
The wavelengths will be calculated for the Balmer and Lyman series and then
compared to those generated by the computer attached to the scanning
spectrophotometer.
Computer Output from a Scanning Spectrophotometer
The peaks on the spectrograph correspond to the energy changes
of the electrons for the Hydrogen atom.
PART B: Emission spectrum of other compounds using
The STAR Spectrophotometer.
1. View the line spectrum through the STAR Spectrophotometer
- point slit towards the light and view to the right.
2. In the hallway, verify that the scale is lined-up accurately by looking
at the fluorescent light. In addition to other lines, you should see a
green doublet for mercury at ~570 nm (the scale on the bottom).
3. Measure the line spectrum of the gas tubes set up near chalkboards.
Note: The fastest/easiest way to do this is have one partner view the lines
and the other write down the observations.
4. Compare your results with NIST literature values.
For the fluorescent light compare it to the element mercury.
Atomic Spectra of Noble Gases
Room 201
& 212
Helium
Room 201
& 212
Neon
Room 201
only.
212 Students
Road Trip!
Argon
Room 201
only.
212 Students
Road Trip!
Krypton
Room 212
only.
201 Students
Road Trip!
Xenon
The Atomic Spectra will be determined for the Noble Gases
by looking at the gas discharge tubes.
The Periodic Table
A period is a horizontal row
of elements in the periodic table.
Atomic numbers increase from left
to right across the table.
There are 7 periods.
A group (also called a family) is
a vertical column in the periodic table.
Elements in a given group have similar
electronic configurations for their
valence shell electrons, and so they
have similar chemical properties.
Atomic numbers increase from top to
bottom.
There are 18 groups.
Periodic Properties
By looking at the relationship
between the chemical reactivity of
magnesium, aluminum, silicon
calcium & zinc and their positions
on the periodic table, we hope to
discover periodic trends within the
3rd & 4th period & the alkaline
earth metal group (family).
Magnesium, 12
Aluminum, 13
Calcium, 20
Zinc, 30
*
*
*
**
Silicon, 14
Some well known periodic trends.
Magnesium, Mg (Z=12)
Properties: an alkaline earth metal, silvery white, fairly tough,
oxidizes slowly in air, burns rapidly in air with a brilliant white
flame. Normally magnesium is coated with a layer of oxide, MgO,
that protects magnesium from air and water.
Available in several forms including chips, granules, powder, rod,
foil, sheet, rod, turnings, and ribbon.
Magnesium, Mg (Z=12)
Properties: a bright white metal that
oxidizes slowly in air, burns rapidly
in air with a brilliant white flame,
2 Mg(s) + O2(g) → 2 MgO(s)
reacts with water at room temperature,
Mg(s) + H2O(l) → Mg(OH)2 (aq)
and reacts with dilute acids with the
liberation of hydrogen gas
Mg (s) + HCl(aq) → MgCl2 (aq) + H2(g)
Magnesium
burns with a
bright white flame.*
does not appear to react with dilute
aqueous alkaline solutions.
*Do NOT look directly
at the magnesium flame.
Aluminum, Al (Z=13)
Properties: a silvery-white
metal that can be highly
polished. It is light, nontoxic
(as the metal), a good
conductor of heat and
electricity, nonmagnetic and
nonsparking.
Aluminum is ductile and malleable and can be drawn into wire
and rolled into sheets. Pure aluminum is soft and lacks strength,
but alloys with small amounts of copper, magnesium, silicon,
manganese, and other elements have very useful properties.
Occurrence: Widely distributed and it is third in abundance on
earth after oxygen and silicon.
Aluminum, Al (Z=13)
Reactions: Aluminum reacts rapidly with the oxygen in air to form
aluminum oxide,
4 Al (s) + 3 O2 (l)→ 2 Al2O3(s)
Because the surface of aluminium metal is covered with this thin layer
of oxide, it is actually protected from further attack by oxygen. So,
aluminum metal does not normally react with air or water.
If the oxide layer is damaged, the aluminium metal is exposed to
attack, even by water. Aluminium metal dissolves in dilute
hydrochloric acid
2Al(s) + 6HCl(aq) → 2Al3+(aq) + 6Cl- (aq) + 3H2 (g)
Aluminium dissolves in sodium hydroxide with the evolution of
hydrogen gas, H2, and the formation of aluminates [Al(OH)4]2Al(s) + 2NaOH(aq) + 6H2O(l) → 2Na+(aq) + 2[Al(OH)4]-(aq) + 3H2(g)
Silicon, Si (Z=14)
Properties: a semi-metallic element,
dark grey with a bluish tinge; amorphous
silicon is a dark brown powder.
Elemental silicon transmits more than
95% of all wavelengths of infrared and
and has been used in lasers to produce
coherent light at 456 nm.
Occurrence: Silicon is present in the sun and stars and is a principal
component of a class of meteorites known as aerolites.
Silicon makes up 25.7% of the earth's crust by weight, and is the
second most abundant element, exceeded only by oxygen.
Silicon, Si (Z=14)
Reactions: The surface of lumps of
silicon is protected by a very thin layer of
silicon dioxide, SiO2. This renders silicon
insoluble in water and most acids.
Silicon does dissolve in hydrofluoric acid forming
fluorosilicic acid,
Si(s) + 6 HF (aq) → 2 H2 (g) + H2SiF6 (aq)
Silicon dissolves in sodium hydroxide forming sodium
silicate,
Si (s) + 2 NaOH (aq) + H2O (l) → 2 H2 (g) + Na2SiO3 (aq)
and highly complex species containing the anion [SiO4]4Si (s) + 4NaOH (aq) → [SiO4]4- (aq) + 4Na+ (aq) + 2H2 (g)
Calcium, Ca (Z=20)
Properties: an alkaline earth
metal, silver-white, which
tarnishes slowly in air and is
approximately as hard as tin.
Occurrence: Widely found as its carbonate in rocks,
chalk, limestone, and marble, and as mixed carbonates in
dolomite, gypsum, CaSO4.2H2O, fluorite, CaF2, apatite,
Ca5(PO4)3, diopside, CaMg(SiO3)2, and lime feldspar,
CaAl2Si2O8.
The soluble calcium salts are responsible for the hardness
of natural spring water.
Calcium, Ca (Z=20)
Reactions: highly reactive chemically,
oxidizes slowly in air, burns rapidly
when heated in air to form calcium
oxide,
2 Ca (s) + O2(g) → 2 CaO(s)
reacts with water to form calcium
hydroxide and hydrogen gas,
Ca(s) + 2 H2O(l) → Ca(OH)2(aq) + H2(g)
and reacts with dilute acids with the
liberation of hydrogen gas,
Calcium
burns with a
light red glow.
Ca(s) + HCl(aq) → CaCl2(aq) + H2(g)
Zinc, Zn (Z=30)
Properties: a transition
metal: bluish-white &
lustrous. Brittle at ambient
temperatures, but malleable
at 100-150 oC.
Occurrence: available in
many forms including dust,
foil, granules, powder, pieces,
shot, and a mossy form.
Flame Test: burns with a
light green glow.
Zinc, Zn (Z=30)
Reactions: When exposed to the atmosphere, zinc reacts with oxygen to form zinc
oxide, which reacts with water molecules in the air to form zinc hydroxide. Finally
zinc hydroxide reacts with carbon dioxide in the atmosphere to yield a thin,
impermeable, tenacious and quite insoluble dull gray layer of zinc carbonate which
adheres extremely well to the underlying zinc.
2 Zn(s) + O2(g) → ZnO(s) + H2O(g) → Zn(OH)2 (s) + CO2(g) → 2 ZnCO3(s)
when the zinc carbonate surface is scratched, the underlying zinc reacts with water
with the liberation of hydrogen gas:
Zn (s) + 2 H2O(l) → Ca(OH)2(aq) + H2(g)
and reacts with dilute acids with the liberation of hydrogen gas:
Zn(s) +2 HCl(aq) → ZnCl2(aq) + H2(g)
and in weak basic solutions, it reacts to form zinc hydroxide, a white precipitate:
Zn(s) +2 NH4OH (aq) → Zn(OH)2(s) + H2(g)
but in stronger basic solutions, this hydroxide is dissolved to form soluble zincates.
Zn(OH)2(s) + 2 OH- (aq) → Zn(OH)42-(aq)
Checkout – (All items checked out should be returned)
STAR Spectroscope
Set of Crayons ROYGBV
1 bottle of phenolphthalein
1 flint striker
5 vials with metals: Mg, Al, Si, Ca & Zn
1 piece of sandpaper
6M HCl in a squeeze bottle
6M NaOH in a squeeze bottle
In Lab
Computerized scanning spectrophotometer – 1 setup in 212
Gas discharge tubes (for viewing by STAR spectroscope)
He & Ne on in both rooms. Ar & Kr in 201. Xe in 212.
All students
View Scanning Spectrophotometer for Part A in Room 212.
TAs will let you know when to go to see the demonstration.
View Gas Discharge tubes for Part B, located near the chalkboards.
Do tests on metals for Part C at your lab bench.
Hazards:
6M HCl – strong acid, corrosive (use solid NaHCO3 on spills)
6M NaOH - strong base, corrosive
Phenolphthalein – laxative effect if swallowed
Bunsen Burner – open flames
Waste:
Liquid waste - all waste, metals, acid & rinses.
For November 17-21
Due: Atomic Spectra & Periodic Properties Handout
(Note: Page 159 counts as your calculations page.
That is, if calculations are shown on p159,
then you do not have to do
an additional calculations page.
Reactor Trip in Class November 17-21 will take the full 3 hours.
Reminder: You must have your student id to go to the reactor.
Also: NO backpacks, NO cell phones & NO electronic devices
are allowed in the reactor!
Read: Radiochemistry (pp 119-136) in Lab packet.