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Grade 11
Unit 4
SCIENCE 1104
ATOMIC STRUCTURE
AND PERIODICITY
CONTENTS
I. CONTRIBUTORS TO A CONCEPT . . . . . . . . . .
2
DEMOCRITUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
JOHN DALTON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
J. J. THOMSON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MARIE CURIE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ERNEST RUTHERFORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NIELS BOHR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ERWIN SCHRODINGER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
JAMES CHADWICK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
3
8
9
10
12
14
15
II. MODERN ATOMIC STRUCTURE . . . . . . . . . . . 21
ATOMIC SPECTRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
BOHR MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
MODERN MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
III. ATOMIC PERIODICITY . . . . . . . . . . . . . . . . . . . 47
PERIODIC LAW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
DMITRI I. MENDELEEV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
IV. NUCLEAR REACTIONS . . . . . . . . . . . . . . . . . . . 55
NATURAL RADIOACTIVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
NUCLEAR ENERGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Author:
Editor:
Illustrators:
Harold Wengert, Ed.D.
Alan Christopherson, M.S.
Alpha Omega Graphics
804 N. 2nd Ave. E., Rock Rapids, IA 51246-1759
© MM by Alpha Omega Publications, Inc. All rights reserved.
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ATOMIC STRUCTURE AND PERIODICITY
are all the other isolated elements what they are
and why are they separated from one another? Why
are they found where they are found and what
accounts for their peculiar qualities?
Scientists thought they had succeeded in breaking down matter to its last ultimate unit: that is, the
atom. In an article which appeared in a national
magazine, a writer on this subject was introduced by
the editor of that magazine as “one of the nation’s
foremost interpreters of modern science.” This modern authority on science then wrote that the Greeks
knew the atom but they did not know what we know
about the atom nor of its infinite smallness. Then
this writer continues by making a startling statement asserting that a teaspoonful of water contains
a million billion trillion atoms. We can repeat these
figures, but no one can comprehend what they mean.
And this writer then says, “We now have learned
that this infinitely tiny atom is composed of still
smaller parts which form a microscopic universe in
which there is action, energy and motion similar to
that of our own solar system.
In everyday language we speak of dead matter,
and, of course, it is dead in the sense that it does not
have in it what we call the germ of life, nor can it
propagate itself. But it is not dead in the sense that
it is inactive or absolutely static. In a lump of socalled dead matter, there are countless billions of
atoms, each one an active universe, a bundle of energy and force beyond all comprehension, as we have
learned since the atomic bomb has come into existence.1
Genesis 1:1 states: “In the beginning God created the heavens and the earth.” What does this
verse mean? Dr. Alfred M. Rehwinkel in his book,
The Wonders of Creation, gives us his explanation.
In view of what occurred on the six days of the
creation week, the heaven and the earth in this connection can only mean that on the first day God
began by the creation of matter out of which He
formed the things that were made on the days that
followed. God began the creation by first providing
himself with the material out of which all other
things were formed. Matter is not eternal, as the
ancient Greek philosophers and the modern evolutionists assume. Matter had its beginning with God;
He created it out of nothing; We first filled the
absolute vacuum of nothingness with raw, unsystematized matter. There is no other possible source
for the origin of matter. Dead matter could not have
created itself.
But that raises the next important question:
namely, What is matter? What is the essence of the
substance out of which heaven and earth were
made?
On the one hand, matter might be defined as a
combination of a number of chemical substances
which combined according to very specific laws to
form that something which we call matter, but that
leads to the next question: that is, What is the origin
of the individual chemical substances which are
combined to form matter? How did the laws come
into being which cause them to combine in a given
order? Science has isolated over a hundred separate
substances which are basic or simple and do not consist of combinations of other substances, but how did
they come to be just what they are? Why is gold gold,
and silver silver, and uranium uranium, and why
This LIFEPAC® will guide our exploration of
the history of atomic theory and develop some
ideas about our modern model of the atom.
OBJECTIVES
Read these objectives. The objectives tell you what you will be able to do when you have
successfully completed this LIFEPAC.
When you have finished this LIFEPAC, you should be able to:
1.
Develop a time-event sequence leading to our present atomic model.
2.
Identify eight key scientists and explain their contributions to atomic theory.
3.
Develop the theory of modern atomic structure.
4.
Develop and explain the periodicity of atomic structure.
5.
Explain nuclear reactions.
Rehwinkel, Alfred M. The Wonders of Creation; Bethany Fellowship, Inc. Minneapolis, Minnesota, 1974, pages 50-51.
1
1
I. CONTRIBUTORS TO A CONCEPT
This section is designed to help you get a better idea and appreciation for eight scientists who made
great contributions to the development of our present-day atomic theory. Information on each scientist is
taken from the “Atomic Pioneer Series.”
United States Energy Research and Development Administration
Technical Information Center
Oak Ridge, TN 37830
The three-volume set is available from ERDA.
SECTION OBJECTIVES
Review these objectives. When you have completed this section, you should be able to:
1.
Develop a time-event sequence leading to our present atomic model.
2.
Identify eight key scientists and explain their contributions to atomic theory.
2.1
Identify and locate the three main particles of atoms.
2.2
Use the atomic mass and atomic numbers of the different elements.
VOCABULARY
Study these words to enhance your learning success in this section.
alpha particle
atomic mass
atomic number
beta particle
electrons
gamma
ion
isotopes
neutrons
nucleus
protons
quantum
radioactive
spectrum
DEMOCRITUS
Democritus was the world’s first great atomic
philosopher. He was born in Abdera, Thrace,
around 460 B.C. and died, place unknown, about
380 B.C.
ter consisted of particles so small that nothing
smaller could be imagined.
These particles were indivisible. The word atom
itself means that which cannot be cut. These atoms
were eternal, unchangeable, and indestructible.
They differed from each other in physical shape,
and this difference allowed them to form different
substances.
Democritus’ theory of atoms led him to
expound an explanation of the world that was completely mechanical. He reasoned that no such thing
as spirit existed apart from matter. He postulated
special “soul” atoms. The universe was the blind
result of swirling atoms. Through their motions
these atoms clumped together to form worlds.
Biographical details. After studying under
Leucippus in Abdera, Democritus resolved to spend
his inheritance in research abroad. He traveled
widely, studying in Egypt for five years and then
journeying to Chaldea, Babylon, Persia, and possibly to India.
Democritus was interested in all branches of
knowledge and specialized in mathematics, astronomy, and medicine. He lived in the shadow of
another Greek philosopher, Socrates. Democritus
once visited Athens and saw Socrates, but he was
too shy to introduce himself.
He wrote many books, but they did not survive.
We know of them because of references made to
them by other writers. His interest in ethics led
him to write proverbs, the accumulated wisdom of
his people. He was a cheerful lover of knowledge,
and he lived to the age of eighty.
Contribution to atomic science. Although
long overshadowed by Socrates, his contemporary,
Democritus nevertheless was the most successful
of the Greek philosopher-scientists in the correctness of his theories.
In line with the Greek basis of knowledge, his
ideas were derived from deductive reasoning, not
from experimenting and testing. Yet his view of the
world was much closer to our twentieth-century
concepts than the views of most other Greek
philosophers of that time.
Scientific achievements. For Democritus,
the world was made of only two things: the vacuum
of empty space and the fullness of matter. All mat2
Answer these questions.
1.1
Who was the first to propose the idea of atoms? __________________________________________
1.2
In what century was the concept of atoms first proposed? _________________________________
1.3
What was Democritus’ academic preparation ____________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
1.4
How did Democritus account for differences in matter? ___________________________________
___________________________________________________________________________________
1.5
Who was Democritus’ famous contemporary? ____________________________________________
JOHN DALTON
John Dalton, an English chemist, was born in
Eaglesfield, Cumberland, England, on September 6,
1766, and died in Manchester on July 27, 1844. He
is considered the father of modern atomic theory.
Biographical details. Dalton was the son of a
poor weaver. His parents were Quakers (Society of
Friends) and he was a devout member of that faith.
He received his early education from his father
and at a Quaker school in his hometown. When his
teacher retired, Dalton replaced him. He was then
twelve years old.
He remained a teacher most of his life. When
he was twenty-seven, he moved to Manchester
and taught college until the college was moved.
He then became both a public and private teacher
of mathematics and chemistry, and he worked in
his laboratory when he was not teaching.
Scientific achievements. Dalton’s first scientific work was in meteorology. He kept weather
records for fifty-seven years. He wrote a book about
weather when he was twenty-seven years old. In
his work, Dalton deduced that gases were composed of particles of matter, just as he thought
solids were. He also made the first study of color
blindness, a subject of personal interest since he
himself was color blind.
His lasting work was in the field of atomic
chemistry. He studied Newton and Boyle and
experimented with gases and Proust’s Law of
Definite Proportions. The Law of Definite
Proportions states that substances combine in predictable proportions. When excess reactants are
used, the excess becomes leftovers.
Figure 1: The Law of Definite Proportions states that when excess reactants are used,
the excess is not combined and becomes “leftovers.”
3
Figure 2: The Law of Definite Proportions Interpreted in Terms of Dalton’s Atomic Symbols
He formulated his own law of multiple proportions in 1803, based on his observation that the
same elements combine in different proportions to
produce different substances.
Figure 3: The Law of Multiple Proportions
He proposed his atomic theory and published
his ideas in a book, New Systems of Chemical
Philosophy in 1808. He maintained that all matter
is made of invisible atoms, that atoms are alike in
everything except their mass (or weight), that in
chemical reactions atoms preserve their identity
and are not destroyed, and that only whole atoms
may combine.
Figure 4: According to Dalton’s atomic theory, only whole atoms may combine.
The second scheme is not possible.
4
He tried to work out the relative masses of
atoms; but his calculations were wrong, although
the principle was correct. He was, however, the first
to establish a table of atomic masses, with hydrogen, the lightest atom, as the standard.
ic hypothesis from Democritus and Newton to his
own day, primarily because he based his theory on
scientific observation rather than on philosophical
speculation.
After Dalton’s work was published, it was widely accepted in a short time and eventually his
atomic theory became the basis of all chemistry.
Contribution to atomic science. Dalton
occupies an important place in the history of atom-
Answer this question.
1.6
Who is considered the father of atomic theory? __________________________________
Explain this activity.
1.7
Law of Multiple Proportions ____________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
1.8
Law of Definite Proportions ____________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
1.9
Dalton’s model of the atom ____________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Do this exercise.
These supplies are needed:
9 samples of pure elements (sulfur powder, zinc powder, magnesium ribbon, iron,
copper, lead, silver, etc.)
reference textbook
Science LIFEPAC 1103
a chemistry handbook
Follow these directions and record your data in the table. Place a check in the box
when the step is completed.
❏ 1. Get some samples of pure elements from the shelf or from your teacher.
❏ 2. From the observations you can make and with the use of a handbook, reference text, and
Science LIFEPAC 1103, complete the following chart of properties.
5
Data Table 1
Element
Symbol
Physical State
at 25°C
Color
Magnetic
Yes or No
Atomic
Mass
Other
Properties
Adult check ___________________
Initial
Date
As is obvious from the preceding data table, the
elements are all different. Apparently then, the
atoms that make up the elements must be all different. The macroscopic properties we saw and
measured in the previous exercise are really the
sum of the properties of the individual atoms. Let’s
investigate a few more properties of four specific
elements.
Try this experiment.
These supplies are needed:
tin can lid with 4 indentations
support stand and ring
bunsen burner or propane burner
sample of iron, copper, magnesium, and lead
Follow these directions and answer the questions. Place a check in the box when the
step is completed.
❏
❏
❏
❏
❏
1.
2.
3.
4.
5.
Secure the ring stand and ring.
Place the lid on the ring.
Place a peg-sized piece of a solid element in each indentation.
Heat each from above with the lighted burner.
Record all observations in the data table.
6
Cu
Data Table 2
Pb
Mg
Fe
Observation
before Heating
Observation
during Heating
Observation
when Cool Again
Complete these activities.
1.10
Burning can be described as the combining with oxygen to form new products. Are these
products of burning the four elements the same? _______________
1.11
Do all four of the elements combine with oxygen in the same way? _______________
1.12
Explain your answers in 1.10 and 1.11. _________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
Try this experiment.
These supplies are needed:
2 vinyl strips
2 acetate strips
masking tape
2 40-cm nylon strings
❏
❏
❏
❏
❏
1.13
1.14
1.15
1.16
1.17
1.18
Follow these directions and answer the questions. Place a check in the box when the
step is complete.
1. Thoroughly wash and blot dry the vinyl and acetate strips.
2. Near one end label the vinyl strips V-1 and V-2.
3. Near one end label the acetate strips A-1 and A-2.
4. Fasten separate 40-cm nylon strings to the center of V-1 and A-1.
5. Hang these strips from a table or chair so they are free to move around in a circle.
What happens when the unmarked end of V-2 is brought near the unmarked end of V-1?
_______________________________________________________________________________________
What happens when the unmarked end of V-2 is brought near the unmarked end of A-l?
_______________________________________________________________________________________
What happens when 1.13 and 1.14 are repeated with A-2 instead of V-2?
_______________________________________________________________________________________
Now rub the unmarked ends of both vinyl strips with woolen cloth, first V-1 and then V-2.
Bring the two rubbed ends near each other. Do they repel or attract?
_______________________________________________________________________________________
Rub the unmarked ends of A-1 with tissue paper and V-2 with wool cloth. Bring the two rubbed
ends together. Did they attract or repel? __________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Reverse the process in 1.17 and use A-2 and V-1. Did the two strips attract or repel?
_______________________________________________________________________________________
7
1.19
From your data and observations complete the following summary:
Combination
Attract or Repel
V-1 and V-2
a. ______________________________
V-1 and A-2
b. ______________________________
A-1 and V-2
c. ______________________________
A-1 and A-2
d. ______________________________
1.20
a. Since the same procedure was used to charge both vinyl strips does each have the same
charge? __________
b. Do both acetate strips have the same charge? __________
c. Do the acetate strips have the same charge? __________
d. Do like charges attract or repel? __________
e. Do unlike charges attract or repel? ____________________
1.21
Experiments have consistently shown that the acetate strip is positive (+) and the vinyl strip
is negative (–). Restate the idea of 1.20 in terms of positives (+) and negatives (–).
_______________________________________________________________________________________
_______________________________________________________________________________________
1.22
a. How many different kinds of electricity do you think the above evidence suggests?
____________________
b. Explain. ___________________________________________________________________________
___________________________________________________________________________________
J.J. THOMSON
Joseph John Thomson, British physicist and
discoverer of the electron, was born at Cheetham
Hall near Manchester on December 18, 1856, and
he died in Cambridge on August 30, 1940.
inside the tube. He measured the deflections in
magnetic and electrical fields and showed that the
rays were streams of negatively charged particles.
Thomson did not measure the size of the negative
charge; that discovery was left to Robert Millikan
after 1910.
Then Thomson measured the ratio of the
charge of the cathode-ray particles to their mass.
He concluded that if the charge was equal to the
minimum charge of ions, then the mass of the particles was only a small fraction of the mass of a
hydrogen atom and that the cathode-ray particles,
electrons, were smaller than atoms. For this discovery he was awarded the 1906 Nobel Prize in
physics.
Biographical details. Thomson entered college at fourteen. When he was only twenty-seven
years old, he succeeded Lord Rayleigh as professor
of physics at Cambridge University. He became
head of the Cavendish Laboratory and guided it
into leadership in the field of subatomic physics for
over thirty years. In 1908 he was knighted. He was
a gifted leader, and seven of his research assistants
were themselves awarded Nobel Prizes. His son
and pupil, Sir George Paget Thomson, also won the
Nobel Prize in physics in 1937. Thomson died just
before World War II and was buried near Isaac
Newton in Westminster Abbey.
Figure 5:
The Thomson
Model of
the Atom:
the “Raisin
Pudding”
Model.
Scientific achievements. In 1895 Thomson
began to investigate the mysterious rays emitted
when electricity passes through an evacuated glass
tube. Because they originated from the cathode, the
negative electrical pole in the tube, the rays were
called cathode rays. No one had succeeded in
deflecting them by an electric field. Other scientists believed that cathode rays were like light
waves, but Thomson believed them to be tiny particles of matter.
He built a cathode-ray tube in which the rays
became visible as dots on a fluorescent screen
8
Thomson had opened the door to research on
subatomic particles. He believed the electron was a
universal component of matter and suggested that
the internal structure of the atom was a positively
charged space with electrons sprinkled throughout,
much like raisins sprinkled through pudding.
Thomson engaged in another important discovery with his work on “channel rays,” which are
streams of positively charged ions. He deflected
these rays by magnetic and electric fields and found
that ions of neon gas fell on two different spots of a
photographic plate, as though they were a mixture
of two types that differed in charge or mass or both.
This finding was his first indication that nonradioactive elements might have isotopes: atomic
varieties of a single element, which differ only in
their mass.
Contribution to atomic science. Thomson’s
work on cathode rays proved the existence of the
electron and led to the study of subatomic particles. Furthermore, when he discovered how to identify isotopes of the chemical element neon 20 and
neon 22, he showed scientists that nonradioactive
isotopes existed.
Complete these activities.
1.23
1.24
1.25
1.26
Describe Thompson’s concept of the atom. _______________________________________________
_______________________________________________________________________________________
Name the apparatus Thomson used to detect electrons. ___________________________________
Describe the difference between neon 20 and neon 22. ____________________________________
_______________________________________________________________________________________
Prior to Thomson’s discovery, electric charge was thought to occur in an infinite range. Explain
the significance of Thomson’s concept of the electron. _____________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
MARIE CURIE
Marie Sklodowska Curie, a Polish-French
chemist, is the only person to have won two Nobel
Prizes in science. She was born in Warsaw, Poland, on
November 7, 1867, and died in Haute Savoie, France
on July 4, 1934.
who, with her husband Frederic Joliot, would win the
1935 Nobel Prize in chemistry.
When Pierre was killed in a street accident in
1906, he was succeeded as professor of physics at the
Sorbonne by Marie, the first woman ever to teach
there. She overcame many professional obstacles, but
she could not overcome all prejudices against women
working as scientists. Though she was nominated to
the French Academy, she lost by one vote because she
was a woman.
However, in 1911 she was awarded another Nobel
Prize in chemistry for research that she and Pierre
had done in the discovery of radium and of polonium,
which she named for her native Poland.
In World War I she interrupted her work to drive
an ambulance on the battlefields of France. After the
war, she spent her years supervising the Paris
Institute for Radium, which she founded.
In honor of Marie and Pierre Curie, the quantity
of any radioactive substance that emits particles at
the same rate as does one gram of radium (37 billions
per second) is called a curie.
Biographical details. Marie Sklodowska’s
father was a Polish physics teacher and her mother
was the principal of a girls’ school. When her parents
died, she followed her older brother and sister to
Paris. She enrolled at the Sorbonne, living an impoverished existence but graduating at the top of her
class.
In 1894, she met the French chemist, Pierre
Curie. They married a year later on July 26, 1895.
The two became fascinated with the discoveries of Xrays by Roentgen and of radioactivity by Becquerel.
Pierre abandoned his own research, and for the final
seven years of his life, he served as his wife’s collaborator. Together they studied radioactivity in uranium
and isolated two new elements, radium and polonium, for which they received the 1903 Nobel Prize in
physics jointly with Becquerel.
The Curies lived modestly, using all their earnings to pay for shipping tons of waste ore, rich in uranium, from abandoned mines in Bohemia to the
physics school where they conducted their research.
They had two daughters. One was Irene, a scientist
Scientific achievements. After the discovery of
X-rays, the Curies undertook a systematic study of
the radioactive properties of pitchblende, an ore of
uranium. Applying Pierre’s discovery of piezoelectricity to the measurement of radioactivity in uranium,
9
In July, 1898, after years of grueling experiments
in their shed, they isolated a tiny amount of a new,
intensely radioactive element, which they named
polonium. In December, 1898, they discovered another intensely radioactive substance, radium in such
small quantities that it could be detected only as a
trace impurity. Now they wanted to produce radium
in visible quantities, and for four years they purified
tons and tons of ore into small samples of pure radium. By 1902 they had prepared a tenth of a gram of
radium from all the tons of uranium shipped to their
laboratory.
they found that some uranium ore must contain elements much more radioactive than uranium. They
performed these experiments in a wretched little
shed that the School of Physics had given them. It
was suffocatingly hot in summer, brutally cold in winter, and the roof leaked. Their precision instruments
were often affected by the humidity and the temperature changes.
Marie Curie had said of this time,”… And yet it
was in this miserable old shed that the best and happiest years of our life were spent, entirely consecrated to work. I sometimes passed the whole day stirring
a mass in ebullition, with an iron rod nearly as big as
myself. In the evening I was broken with fatigue. In
our poor shed there reigned a great tranquillity:
sometimes, as we watched over some operation, we
would walk up and down, talking about work in the
present and in the future; when we were cold, a cup
of hot tea taken near the stove comforted us. We lived
in our single preoccupation as if in a dream.”
Contribution to atomic science. The discovery of radium and polonium by Marie and Pierre
Curie and their research on radioactivity laid the
foundation for new discoveries in nuclear physics and
chemistry. Scientists would follow close on their trail
to discover other radioactive elements.
Complete these activities.
1.27
1.28
1.29
1.30
1.31
An ore of uranium is ______________________________ .
The discoverer of X-rays was a. ____________________________________ , and the discoverer of
radioactivity was b. _____________________ .
The two elements isolated by the Curies were a. ____________________________________ and
b. ____________________________________ .
The school in Paris at which Marie Curie was the first woman teacher was ________________
____________________ .
The achievements of which Pierre and Marie Curie were awarded Nobel Prizes were the
a. ______________________________ and the b. ______________________________ .
ERNEST RUTHERFORD
Ernest Rutherford, a British physicist whose
contributions to science of the theory of the nuclear
atom brought him the title, “father of nuclear science.” He formulated the theory of radioactive disintegration of elements, identified alpha and beta
particles, and devised the theory of the nuclear
structure of the atom. He was born on a farm near
Nelson, New Zealand, on August 30, 1871, and died
in London on October 19, 1937.
Manchester University and Cambridge where he
remained until his death.
He won many honors for his scientific achievements. He was knighted in 1914, and in 1931 was
named First Baron Rutherford of Nelson.
Scientific achievements. Rutherford’s great
contributions to science began at McGill University
with work in the field of radioactivity. There he
reported on the discovery that rays given off by
radioactive substances are of several different
kinds. He called the positively charged ones alpha
rays and the negatively charged ones beta rays.
The names are still used, but today the rays are
known to be speeding particles and are called
alpha particles and beta particles. When Paul
Villard discovered in 1900 that some rays were not
affected by a magnetic field, Rutherford proved
that these consisted of electromagnetic waves,
which he called gamma rays.
Biographical details. Rutherford was the son
of a wheelwright and farmer. As a child he helped
his father dig potatoes on the farm. He was a promising student and won scholarships to Canterbury
College in New Zealand and to Cambridge
University in England, where he worked under J. J.
Thomson.
At McGill University in Montreal from 1898 to
1907, Rutherford continued work he had begun in
the field of radioactivity. Then he returned to
10
Figure 6: Rutherford Gold Foil Experiment.
Notice that the particles (bullets) are scattered but
most go right on through the “solid” gold foil.
Rutherford and Frederick Soddy collaborated
in research on radioactive disintegration. They
believed that, starting with uranium, each radioactive element decays, or breaks down, into a daughter element, and that this daughter element breaks
down into another, and so on. The last element
formed is lead.
Figure 7: Rutherford’s Gold Foil Experiment
Rutherford began to study how alpha particles
are scattered by thin metallic sheets.
When he fired alpha particles at gold foil, most
of the particles passed through unaffected. Some of
them, however, scattered at large angles, which
meant that somewhere in the foil was a massive
charged region that deflected the positively
charged alpha particles. Rutherford said this finding was “almost as incredible as if you fired a fifteen-inch shell at a piece of tissue paper and it
came back and hit you.”
Rutherford went to Manchester University in
1909 and established a center for the study of
radioactivity. He proved that the alpha particle was
a helium atom with its electrons removed. (Later
he said that the simplest positive rays must be
those obtained from hydrogen and that these must
be a fundamental positively charged particle,
which he called a proton.)
From this research Rutherford evolved the
nuclear theory, the greatest of all his contributions
to physics. He suggested that the atom contains a
very tiny nucleus at its center, which is positively
charged and contains all the protons of the atom
and therefore almost all its mass. Very light negatively charged electrons, posing little barrier to
alpha particles passing through the atom, make up
the outer regions. His was dubbed the “open
spaces” model.
In 1908 Rutherford won a Nobel Prize for “his
investigations of the chemistry of radioactive substances.” In a letter to his mother he said that the
prize was very acceptable, “both as regards honour
and cash.”
The nuclear theory was not Rutherford’s sole
contribution to science. With Hans Geiger he used
a scintillation counter to measure radioactivity.
They counted the flashes (scintillations), each of
which signified an emitted particle, on a zinc sulfide screen and determined that a gram of radium
emitted 37 billion alpha particles a second. This
fact is the basis for the unit called the curie.
In 1917 Rutherford resumed his research in
nuclear models. In 1919 he succeeded in disintegrating nitrogen nuclei by alpha particle bombardment, producing charged hydrogen atoms and oxygen at the same time. With this act he accomplished the first man-made “nuclear reaction,” and
by 1924 Rutherford accomplished the feat of knocking the protons out of nuclei in most of the lighter
elements.
Rutherford was a marvelous teacher and
infected his students with his own enthusiasm for
scientific research. (Among his many illustrious
students were Ernest Marsden, Hans Geiger,
Ernest Walton, James Chadwick, Francis Aston,
John Cockcroft, Henry Moseley, Otto Hahn, and
Frederick Soddy.) His students said of him, “He
had none of the meaner faults and was just as willing to attend to the youngest student and if possible learn from him as … to listen to any recognized
scientific authority. He made us feel as if we were
living very near the center of the scientific universe.”
He had a short temper, which he sometimes
displayed when experiments were not going to his
satisfaction. When things ran along smoothly, he
would walk through the laboratory singing
“Onward Christian Soldiers.”
Contribution to atomic science. Lord
Rutherford contributed the theory of the basic
11
structure of the atom itself. In addition he was the
first scientist in history to produce man-made
atomic disintegration, when he bombarded nitrogen atoms with alpha particles and produced protons. Fellow scientist Niels Bohr said when
Rutherford died that he, like Galileo, “left science
in quite a different state from that in which he
found it.” A physicist once said to Rutherford, “You
are a lucky man…always on the crest of the wave!”
“Well,” Rutherford remarked, “I made the wave,
didn’t I?”
Complete these activities.
1.32
1.33
1.34
1.35
1.36
1.37
1.38
Name the renowned professor under whom Rutherford studied at Cambridge University.
_________________________
Rutherford named three kinds of radioactive emissions. List the emissions and describe
them.
a. emission: __________________________________________________________________________
b. description: ________________________________________________________________________
a. emission: __________________________________________________________________________
b. description: ________________________________________________________________________
a. emission: __________________________________________________________________________
b. description: ________________________________________________________________________
Describe the hypothesis produced by the research of Rutherford and Soddy. ________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Describe the gold foil experiment which led Rutherford to the discovery of the atomic nucleus.
___________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Name the device used for scintillation counting. _________________________________________
NIELS BOHR
Niels Bohr, a Danish physicist, helped develop
the field of quantum physics. He was awarded the
Nobel Prize in physics in 1922 for his atomic theory, which laid the groundwork for later atomic
research. He was born on October 7, 1885, in
Copenhagen, Denmark and died there November
18, 1962.
From Sweden, Bohr came to the United States
where he participated in the Los Alamos atomic
bomb project. He helped organize the first United
Nations Atoms-for-Peace Award two years later.
Scientific achievements. Bohr showed an
early talent for physics. At the age of twenty-two,
he won a gold medal for determining the surface
tension of water.
Working with Rutherford, Bohr studied that
scientist’s nuclear model of the atom. In 1913 he
combined the Rutherford nuclear atom with the
quantum theory of Max Planck to explain how
atoms emitted and absorbed ultraviolet light and
infrared energy.
Studying the hydrogen atom, he concluded that
electrons move in orbits around the atomic nucleus. As long as an electron remains in a given orbit,
no energy is radiated. However, a suitable energy
source can cause the electron to jump to an orbit of
higher energy. When the electron returns to the
lower orbit, the extra energy is liberated as a single quantum (specified quantity) of light or other
form of radiation.
Biographical details. Bohr studied physics at
the University of Copenhagen and received his doctorate in 1911. He went to Manchester University
and worked under Rutherford until he returned to
the University of Copenhagen as physics professor.
In 1920 Bohr became head of the newly created
Institute of Theoretical Physics in Copenhagen,
and he held this position until his death. By the
1920s his institute had become a world center of
atomic physics. There his interpretations of quantum theory were developed.
In 1940 Denmark was occupied by the
Germans, and Bohr fled by fishing boat to Sweden.
When he escaped, he carried with him his Nobel
medal made of gold, which he had melted down in
order to carry it inconspicuously. After the war he
had the medal recast into its original form.
12
Figure 8: Three Different Models of the Nitrogen Atom
Each type of radiant energy is transmitted in
waves with a certain range of frequencies. Bohr
derived equations for calculating the frequencies of
the lines in the spectrum of the hydrogen atom.
Bohr was unable to apply his theory to calculate the
spectrum of atoms more complex than hydrogen;
but he pointed out that in elements heavier than
hydrogen, those possessing more than one electron,
the electrons exist in shells, and the electron content
of the outermost shell determines the chemical
properties of the element.
After Meiter’s and Frisch’s theory of uranium
fission was announced in 1939, Bohr correctly predicted that the isotope uranium 235 was the fissionable isotope.
finally transmuted the enterprise. It was a period
of patient work in the laboratory, of crucial experiments and daring action, of many false starts and
many untenable conjectures, of debate, criticism,
and brilliant mathematical improvision. For those
who participated, it was a time of creation; there
was terror as well as exaltation in their new
insight. It will probably not be recorded very completely as history. As history, its re-creation would
call for an art as high as the story of Oedipus or
the story of Cromwell, yet in a realm of action so
remote from our common experience that it is
unlikely to be known to any poet or historian.”
The Bohr model had problems, however.
Because your radio picks up static from overhead
wires or from an electric mixer, you know that an
accelerating electrical charge emits energy. You may
also know that any object in circular motion is accelerating because the direction of its velocity is changing. When these two bits of knowledge are put
together, the conclusion is that orbiting electrons
should emit energy. However, orbiting electrons do
not emit energy unless they change orbits. If orbiting electrons did emit energy, every object in your
room would foul radio reception; and rather quickly
every atom would lose all its energy and collapse in
on its nucleus, leaving just a very small pile of dust.
This conclusion is the origin of a recurring problem:
Do classical laws of physics and chemistry—
Newtonian laws of motion, for example—apply to
atomic particles?
Contribution to atomic science. Bohr
applied quantum theory to explain the hydrogen
spectrum. Later he prepared a scheme for the
arrangement of electrons in various atoms on the
basis of their radiation spectra.
J. Robert Oppenheimer summed up Bohr’s
contribution in this way: “Our understanding of
atomic physics, of what we call the quantum theory of atomic systems, had its origins at the turn
of the century and its great synthesis and resolutions in the nineteen-twenties. It was a heroic
time. It was not the doing of any one man; it
involved the collaboration of scores of scientists
from many different lands, though from first to
last the deeply creative and subtle critical spirit of
Niels Bohr guided, restrained, deepened, and
Do these activities.
1.39
Name the famous atomic physicist under whom Niels Bohr studied at Manchester University.
_______________________________________________________________________________________
Thomson and Rutherford had each contributed a small bit of understanding to the structure of
the invisible atom. Summarize their contributions to the atomic model and describe the addition made by Niels Bohr.
1.40
Thomson. _____________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
13
1.41
Rutherford ____________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
1.42
Bohr _________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
1.43
Explain why the Rutherford-Bohr model is aptly called the planetary atom.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
1.44
Describe the cause of light emission from atoms. _________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
1.45
Draw one logical inference about emitted light from these statements:
a. Orbits in any given element are fixed energy levels.
b. The frequency (color) of emitted light is related to its energy.
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
ERWIN SCHRODINGER
Erwin Schrodinger (shroi ding er), an Austrian
physicist, shared the Nobel Prize in physics in 1933
with P. A. M. Dirac for their new atomic theory,
which included wave mechanics and prediction of
the positron. He was born on August 12, 1887, in
Vienna, Austria, and died there on January 4,
1961.
of several specific orbits. Around each of these electrons, matter waves spread out in a specified number of wave lengths. For any given element, electrons exist only in certain orbits. In the late 1920’s,
Schrodinger derived the mathematical basis for
this idea, which is called wave, or quantum,
mechanics.
Biographical details. Schrodinger was educated at the University of Vienna. When World War
I broke out, he fought as an artillery officer and
then settled in Germany after the war.
He taught physics at several universities and
in 1927 succeeded Max Planck as professor of theoretical physics at the University of Berlin.
In the early 1930’s he interceded during a Nazi
raid on a Jewish ghetto. He would have been beaten to death, except that one of the Storm Troopers
recognized him and prevented the attack.
When the Nazi rise to power became inevitable,
Schrodinger returned to Austria. When Germany
annexed Austria, Schrodinger fled to Ireland and
taught at the Institute of Advanced Studies in
Dublin. In 1956 he returned to Vienna and
remained there until his death in 1961.
Contribution to atomic science. De Brogile
had postulated that matter at the atomic level possessed characteristics of both particles and waves.
In addition to the matter being minute, it had to be
moving at speeds near the speed of light. Based on
this idea, Schrodinger expressed the behavior of a
particle with a mathematical equation for wave
motion. By combining this mathematical equation
with the quantum theory, the Schrodinger equation
of wave mechanics was derived.
The Schrodinger equation has many applications in the study of the behavior of small particles.
In particular, it was used to explain the spectrum
of atomic hydrogen more exactly than Bohr had
been able to do without introducing the problems
that Bohr had acknowledged with his model.
Scientific achievements. In his research
Schrodinger wanted to combine the Bohr atom
model with de Broglie’s matter waves. In
Schrodinger’s model, the electron can exist in one
14
Complete these activities.
1.46
Describe Schrodinger’s improvement on the Bohr model concept of orbits.
_______________________________________________________________________________________
_______________________________________________________________________________________
1.47
Describe de Broglie’s concept of the nature of matter. _____________________________________
_______________________________________________________________________________________
1.48
De Broglie’s concept applies to matter under two specific conditions. Name the two conditions.
a. ___________________________________________________________________________________
b. ___________________________________________________________________________________
1.49
The Schrodinger equation describes the behavior of a particle in terms of another physical phenomenon. Name the other phenomenon. _____________________________________________
JAMES CHADWICK
Scientific achievements. In 1931 Chadwick
began the experiments that would result in the discovery of the neutron. Frederic and Irene JoliotCurie, daughter and son-in-law of Marie and Pierre
Curie, had reported that when beryllium was bombarded with alpha particles, the resulting radiation from the beryllium caused protons to be emitted from paraffin wax, or from anything else that
contained hydrogen. The kind of radiation produced was unknown, but Chadwick concluded that
the alpha particles were ejecting neutral particles
from beryllium nuclei of sufficient mass to cause
protons to be emitted from the paraffin.
Chadwick performed the Joliot-Curie experiments and analyzed the results using the Geiger
counter, the high-pressure ionization chamber, and
the expansion chamber. With these instruments he
discovered the neutron in 1932.
James Chadwick, English physicist, won the
1935 Nobel Prize in physics for his discovery of the
neutron. He was born in Manchester, England, on
October 20, 1891.
Biographical details. Chadwick graduated
from the University of Manchester and received his
Master of Science degree there. He went to
Germany on a scholarship to study under Hans
Geiger. He was interned in Germany until the end
of World War I.
In 1919 Chadwick went to the Cavendish
Laboratory to work with Rutherford. In 1923 he
became assistant director of research at the laboratory and in 1935 he went to the University of
Liverpool as professor of physics.
During World War II Chadwick worked on the
Manhattan Project in the United States. He
returned to England in 1948 to become master of
Gonville and Caius College at Cambridge
University.
Contribution to atomic science. The discovery of the neutron was of great importance since
this particle was to be used several years later to
initiate a chain reaction.
Complete these activities.
1.50
Describe an alpha particle. _____________________________________________________________
_______________________________________________________________________________________
1.51
Describe the effect alpha bombardment had on beryllium. ________________________________
_______________________________________________________________________________________
1.52
Describe the result of firing a B-B at a bowling ball. ______________________________________
_______________________________________________________________________________________
1.53
Describe the result of firing a bowling ball at a bowling ball. ______________________________
_______________________________________________________________________________________
1.54
Draw a conclusion about the mass of a neutron if it is capable of displacing a proton.
_______________________________________________________________________________________
15
On the basis of what you have learned so far in this LIFEPAC, complete the following data
table.
Data Table 3
Particle
1.55
Electron
1.56
Proton
1.57
Neutron
Charge
Discoverer
The atomic number of an element is defined as
the number of positive charges in the nucleus. The
mass number, or atomic mass, is the number of pro-
Mass Number
Atomic Number
Year
Discovered
Mass
Compared to
a Proton.
Location
in Atom
tons plus the number of neutrons in the nucleus.
Atoms that have the same atomic number but different mass numbers are called isotopes.
14
7
15
7
N
N
Symbol of
Element
Complete these activities.
1.58
Use the preceding definitions to analyze nitrogen isotopes.
a. What is the atomic number of the two isotopes? _______________
b. Why are they equal? _______________________________________________________________
1.59
a. What are the mass numbers? ________ , ________
b. Why are they unequal? _____________________________________________________________
___________________________________________________________________________________
1.60
a. How many electrons does each isotope have? ________ ________
b. How do you know? _________________________________________________________________
___________________________________________________________________________________
Adult check ___________________
Initial
Date
16
17
1.76
1.77
1.78
1.79
1.74
1.75
1.71
1.72
1.73
1.70
1.69
1.64
1.65
1.66
1.67
1.68
1.62
1.63
1.61
1.80
The following crossword puzzle should help you review this section.
1
3
2
4
6
5
7
8
ACROSS
9
1.
The particle of an atom with a negative
charge.
6.
Meaning identical to something else.
7.
When you are on vacation in Florida, you
are __________ a trip.
10
r
12
13
15
Symbol for phosphorus.
9.
The element with an atomic number of 24.
10.
A word meaning dimes, nickels, dollars.
11.
Symbol for the element carbon.
12.
A type of moss or soft coal.
13.
Abbreviation for the number of protons in
an atom.
15.
Boy’s name.
17.
Group of three singers.
19.
Symbol of chromium.
21.
A food similar to a sweet potato.
22.
Element with an atomic mass of 80 and
containing 45 neutrons.
23.
Element with atomic number of 85.
25.
A deceased leader of Red China.
26.
Element with atomic mass of 39 and containing 20 neutrons.
27.
All matter is composed of about 106 different kinds of these.
29.
14
16
17
19
8.
11
e
20
23
26
18
21
24
22
25
27
30
29
31
32
DOWN
1.
To get free from something.
2.
A proton has a _______ mass than an
electron.
The element making up the largest part of
our bones and teeth (symbol)
3.
A place to bury people.
4.
Man’s name.
5.
A penny = _______ cent.
9.
Garment worn over the shoulders.
11.
Formula for carbon monoxide.
13.
Simplest particle of matter still having the
properties of an element.
30.
Dinosaurs lived a long time __________ .
31.
Symbol for element with atomic number of
13.
14.
Symbol for the element with 11 electrons.
16.
Name of a popular breed of cat.
Twenty-four inches is the same as two
__________ .
18.
Positively charged particle of similar mass
to a neutron.
20.
Symbol for radium.
22.
Loud noise.
24.
A drink which can be served warm like
coffee.
25.
A food from cattle.
29.
Symbol for the element with 17 protons.
32.
Adult check ___________________
Initial
Date
18
Review the material in this section in preparation for the Self Test. The Self Test will check
your mastery of this particular section. The items missed on this Self Test will indicate specific
areas where restudy is needed for mastery.
SELF TEST 1
Match these items. Each choice may be used more than once or not at all (each answer, 2 points).
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
1.09
1.010
1.011
1.012
1.013
1.014
1.015
1.016
1.017
1.018
1.019
1.020
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
_____
mass same as proton
most of the mass of the atom
postulated “open spaces” model
negative charge
discovered the proton
father of atomic theory
behavior of like charges
mass 1/1837 that of one proton
equal in number in an atom
is emitted from a cathode-ray tube
taught seven Nobel Prize winners
discovered the electron
positive charge
outside the nucleus
behavior of unlike charges
postulated the quantum atom
makes up the nucleus
discovered the neutron
neutral
“raisin pudding” model
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
protons
protons and electrons
protons and neutrons
neutron
electrons
Chadwick
J. J. Thomson
Bohr
Rutherford
Dalton
attract
repel
Write the letter for the correct answer on each line (each answer, 2 points).
108
1.021
The element ᎏ Ag has _____ protons.
47
a. 108
b. 47
c. 61
d. 107
e. 87
1.022
The man responsible for discovering the “open spaces” structure of the atom is _____ .
a. Millikan
d. Dalton
b. Bohr
e. Einstein
c. Rutherford
1.023
A false statement concerning matter is _____ .
a. matter cannot be subdivided
b. matter is composed of many small particles called atoms
c. matter is mostly empty space
d. all matter contains mass
e. matter is made up of about 100 different types of atoms
1.024
The true statement concerning the atomic nucleus is _____ .
a. it takes up most of the volume of the atom
b. it weighs approximately 10-20 grams
c. it contains protons, neutrons, and electrons
d. it contains most of the mass of the atom
e. it is made up of electrons only
19
1.025
1.026
Carbon 14 has an atomic number of 6. Carbon
a. 14
c.
b. 6
d.
238
The element ᎏ U has _____ neutrons.
92
a. 92
d.
b. 238
e.
c. 330
has _____ electrons.
20
8
184
146
1.027
A symbol for an element _____ .
a. may be used to represent a compound which contains the element
b. is an abbreviation for the name of the element
c. is used to represent 96,500 atoms of the element
d. may be used to represent 22.4 liters of the element
e. is of little use to chemists
1.028
The nucleus of an atom contains _____ .
a. protons, neutrons, and electrons
b. protons and neutrons, (except H)
c. about half of the mass of the atom
d. all of the electrons which are converted to atomic energy
e. different types of particles, depending upon the particular element
1.029
Isotopes are described as follows: Isotopes _____ .
a. are atoms of different elements which have the same mass
b. of a given element have equal numbers of neutrons
c. of a given element have very similar chemical properties
d. of a given element have equal numbers of protons and neutrons
e. are atoms that have gained or lost electrons
1.030
The atomic number of an atom is equivalent to the number of _____ .
a. neutrons
d. protons
b. electrons
e. protons and neutrons
c. alpha particles
48
Score
60
Adult Check
_______________
___________________
Initial
20
Date