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Simple Schooling Atomic Theory ©2011 The Simple Homeschool
1
By J. Anne Huss
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
2
By J. Anne Huss
ATOMIC THEORY
It sounds so mysterious – doesn’t it? Atomic theory conjures up images of secret
science in the 1940’s, the atom bomb, and explosions! But the truth is, atomic
theory is simply the internal structure of the atom. It’s not sinister, secret, or
scary – it’s nothing more than a blueprint!
How we came up with the blueprint for something as small as the atom is quite
another story – and yes – this does involve chalkboards covered with equations,
funky experimental contraptions, and science nerds. Lots and lots of science
nerds!
You’ve probably learned a bit
about the atom before so let’s
just skim over the basics of
the what, why, and how of
atoms before digging deeper.
The first thing to discuss is the definition of an element. An element is a basic
building block of matter. All the known elements are contained in a special chart
called the Periodic Table of the Elements and everything on the table cannot be
broken down into any more parts. For instance – gold is gold. It does not contain
any other element other than gold. Same with silver, copper, tin, iron, cobalt,
uranium and so on.
The best way to describe an element is a fundamental (basic) building block of
other compounds. A compound is a combination of two or more elements. Table
salt is a compound because it contains sodium and chlorine – which when combined
makes sodium chloride – or table salt.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
In order to classify elements we must understand their basic structure and
internal components. An atom is the basic unit of matter but it also has
fundamental components inside of it called protons, electrons, neutrons. These
things inside the atom are called subatomic particles. The specific arrangement of
the subatomic particles is what makes each element unique.
A molecule is a collection of
atoms. For example, water is a
collection of two hydrogen atoms
and one oxygen atom. That’s H2O
– and H2O is a molecule because it
has two atoms – hydrogen and
oxygen. H is an atom, O is an
atom and both H and O are also
elements because they cannot be
broken down into smaller atoms.
They can be broken down into
smaller particles such as protons,
electrons, and neutrons. But
those are called subatomic
particles and are not atoms.
To understand atomic theory you must first understand the subatomic particles
within the atom and where each of these particles can be found. The nucleus is
very small and dense and resides towards the center of the atom. The nucleus is
not a particle like a proton, electron, or neutron; rather it is a place.
A proton is a subatomic particle that resides in the atom; more specifically, it
resides inside of the nucleus. The proton is a positively charged particle. We show
a positive charge by using the plus symbol (+) next to an element.
A neutron has no charge – we call that an uncharged particle. The neutron also
resides inside the nucleus. Don’t get the nucleus and the neutron mixed up. The
nucleus is a place inside the atom, while the neutron is a subatomic particle.
Electrons are probably the most interesting thing about atoms because they don’t
reside inside the nucleus and are free to move about inside the atom. In some
cases, the electrons can even leave the atom and join another atom.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
This is how chemistry is done. Electrons, as
we understand them today, exist in a “cloud
state” and do not occupy a specific place
inside the atom. Electrons are negatively
charged (when we write this we use a minus
sign to show a charge, so an electron would
have a charge of -1). The negative charge on
an electron cancels out the positively
charged proton inside the nucleus.
Now that you have a basic understanding of
the atom and the subatomic particles that reside inside the atom, you should next
understand matter. Matter is anything that has both mass and volume so these two
properties, mass and volume, are used to describe the substances which are
matter. Scientists also say that matter is something that occupies space. That is a
pretty broad definition. In fact, it includes everything you come into contact with
in your daily life. Cars are made of matter, hair, eyes, books, water, and air are all
made up of matter.
Since the beginning of time humans have wondered about
what “stuff” is made of, and over the centuries they came
up with some pretty good, and pretty rotten, ideas about
the concept. Today we use the word atom to describe the
basic and fundamental “stuff”. This word comes from the
ancient Greek word atomos, which means unable to divide or
cut. The ancient Greek philosopher Democritus (who lived
between 460 and 370 BC) and his mentor Leucippus are
generally credited with the naming of these tiny invisible
particles. They also came up with a theory on their basic
characteristics.
Unfortunately, the view held by Democritus and other “atomists” didn’t hold for
long and was generally forgotten until the seventeenth century when scientists
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
began to think about the properties of gases. When these seventeenth century
scientists began to think critically about air, something which is colorless (invisible)
and had no odor, they began to wonder a little more about how one could accurately
describe such a thing. What was “air”? What was it made of? How could they
measure it?
One thing scientists had figured out during this period is that things are made up
of elements and before there were scientists there were alchemists. An alchemist
was a person who practiced alchemy, and alchemy was the “science” of
understanding, deconstructing, and reconstructing matter. It is also used
interchangeable as the pursuit of turning common metals such as lead or copper
into gold.
In 1789 a French scientist named Antoine Lavoisier
discovered that even though matter may change its form or
shape, its mass always remains the same, thus he was the
first to formulate the Law of Conservation of Mass. During
Lavoisier’s time air and water were considered elements, but
he rejected this notion and eventually described the
individual components of air (nitrogen, oxygen, argon) and
water (hydrogen and oxygen). These discoveries, like all
previous discoveries, propelled the thinking and reasoning of
other scientists who were looking to explain what atoms were.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
The next major step in the process of discovering what
atoms were was the theory proposed by an English
schoolteacher named John Dalton, around the year 1803.
His theory states the following:
1. Each element is composed of extremely small particles
called atoms.
2. All atoms of a given element are identical to one
another in mass and other properties, but the atoms
of one element are different from the atoms of
another element.
3. Atoms of an element are not changed into atoms of a
different element by chemical reactions; atoms are
neither created nor destroyed in chemical reactions.
4. Compounds are formed when atoms of more than one element combine, a
given compound always has the same relative number and kind of atoms.
As you have already learned, Dalton’s theory explains that atoms are the smallest
particles of any given element and are the substance which contains and retains
the chemical identity of the element – even during a chemical reaction.
John Dalton based his theory on other chemical laws known to exist at the time –
including the Law of Conservation of Mass and the Law of Constant Composition
which states that the molecular make-up of a substance is always the same,
regardless of how the substance was made or where the substance is found.
Using water as an example we know with certainty that all water molecules contain
2 hydrogen atoms for each oxygen atom, regardless of whether we got it from the
sink or collected it from a mountain stream.
Dalton also deduced from
his observations the Law
of Multiple Proportions,
which states when two
elements can combine to
form more than one compound and the same amount of the first element is used in
each, then the ratio of the amounts of the other element will be a whole number.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
The significance of this law is not important to understand right now but it is the
basis of stoichiometry – or how the products and reactants of a chemical equation
relate to one another. Stoichiometry is a fundamental concept of high school and
college chemistry.
It is important to understand that John Dalton had no direct evidence to support
his theory – instead he relied on chemical observations. He could not see the
oxygen and hydrogen atoms – thus there was really no evidence that atoms actually
existed until more modern times when powerful microscopes were developed.
It is for this reason that atomic theory has changed quite a bit over the past 2
centuries and so we must discuss several simpler models before arriving at the
current theory of atomic structure.
We now know that the atom is not the smallest and most basic fundamental
particle. We know this because inside the atom are electrons, protons, and
neutrons. While this might seem elementary to you, being a student of the 21st
century, it was not at all obvious to scientists in the mid 1800’s.
The first subatomic particle to be discovered was the
electron. Scientists all over Europe had been busy looking
at electrical energy – they knew that some elements could
carry an electrical charge and that charges could be either
positive or negative.
One way in which scientists studied electrical discharge,
which is the giving off of electrical energy, was to partially
empty a glass tube of air and push a voltage through it.
This created a negative charge on one end and a positive
charge on the other and was called a cathode ray. Watch
this animation about cathode rays and JJ Thompson’s
electron discovery.
During this time more scientist were experimenting with subatomic particles and
the new mystery became – How do all these particles fit together inside the atom?
JJ Thompson, who calculated the mass of the electron, also came up with the first
definitive model for the inside of the atom. He called it the “Plum Pudding Model”
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By J. Anne Huss
and thought that electrons were embedded inside the
atom like raisins in a cup of plum pudding.
This theory didn’t last long, mostly because it was
wrong, but also because a
scientist from New Zealand
named Ernest Rutherford proved
with his famous backscattering
experiment that most of the
mass of an atom was
concentrated into a compact nucleus, with electrons
occupying the bulk of the atom's space and orbiting the
nucleus at a distance. This eventually led to the discovery of
protons (the positive charge in the center of an atom), by
Rutherford, and neutrons, by an English scientist named
James Chadwick. Watch this animation about Rutherford’s
backscattering experiments.
Since the discovery of the three major subatomic particles
scientists have learned a lot more about how atoms are
structured. There are in fact, many more sub atomic particles
inside the atom, but only these three are terribly important for
the study of basic chemistry.
With the Plum-Pudding model out, and the backscatter
experiment by Rutherford proving that most of the atom is
empty space, atomic structure evolved into the Niels Bohr
planetary model.
The planetary model is still
used for elementary students
today because it is simple; but
it is not correct. Today we
know that the electrons don’t
“orbit” the nucleus like planets
orbiting the sun, instead they
exist in the “cloud” outside the
nucleus.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Look at the chart below. In the chart you are presented with a compare and
contrast view of each of the subatomic particles. Study the chart before moving
on.
Now let’s talk about each
subatomic particle
individually and how they
are significant in
chemistry.
The proton is a positively charged subatomic particle which
resides inside the nucleus of the atom. The nucleus is the
center mass. Since the mass of subatomic particles is so
small, we use a special unit of measurement called the atomic
mass unit – or AMU to measure it. A proton has a mass of
approximately 1 amu (atomic mass unit). Protons also carry a
charge, in fact they have a charge of +1, which means they
are positive.
The proton is the most important particle because it is what
gives the element its identity. If an element has one proton
it is hydrogen, if it has two it is helium. If it has 14 it is
nitrogen. There is no way a helium atom can have 1 proton
because if it does – it is not helium, it is hydrogen.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Since the protons in the atom dictate which element
it is, this number is used as an identifying marker
and is called the atomic number. So – the number of
protons is the same as the atomic number.
The neutron is an uncharged particle which resides
inside the nucleus with the proton. It too has the
approximate mass of 1 amu. Some students might
wonder what the purpose of the neutron is because
it sort of just sits there and doesn’t seem to do
anything. But it does do something – it helps to hold
the nucleus together! The neutrons are necessary
to prevent the positively charged protons from
repelling each other right outside the nucleus.
The electron is the rock star of subatomic particles
in chemistry. It is the electron which moves around
in a chemical reaction because remember – you can’t
move protons around without changing the element
completely.
The electron has a mass but it is so small that we pretty much
just say it is zero! It also has a charge of -1. Electrons are
located outside of the nucleus in what we call the electron
cloud. The electron cloud is really more of an approximate
place where an electron might be found at any given time, not
an actual point in space.
You now know that it is the arrangement of subatomic
particles which give each atom its individual properties. Now
we want to explore how little differences in the number of
neutrons and electrons can change the element slightly – not
enough to be another element entirely – but enough to have a
significant effect on the way the element behaves in a
chemical reaction.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Recall that the number of protons in the nucleus is the
same as the atomic number and that the atom is naturally
occurring in an uncharged state – so this tells us that the
number of protons equals the number of electrons.
Right off the bat we are going to shake things up a bit
with the neutrons – because the number of neutrons can
change. Earlier you were told that the number of
protons must always be the same, but that is not true
for neutrons or electrons. When we change the number
of neutrons we have a slightly different version of the
same element. This new version is called an isotope.
If the atom has a different number of neutrons than number of protons this means
that the atomic mass of the atom has changed. Recall that both protons and
neutrons have a mass of about 1 amu each. Naturally if the number of neutrons
changes, then the atomic mass of the atom also changes. If you add more neutrons
the atom gets heavier – imagine it is like you picking up a large stone and stepping
on the scale. You’d weight more, right? If you subtract some neutrons then the
atom weighs less – makes sense – if you drop that stone while you’re on the scale,
you lose weight immediately!
The atomic number and the atomic mass number are both included when using
elemental notation. Elemental notion is a visual shorthand way of describing the
number of subatomic particles inside an atom. Elemental notation consists of the
element symbol, the atomic number, the mass number, and charge (if there is one).
It looks like this:
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Students and scientists use elemental notation to determine how many proton,
electrons, and neutrons are inside an atom, as well as which atom it is, and whether
or not it is an isotope, or contains a charge. Atoms with the same atomic numbers
but different mass numbers (have a different number of neutrons) are called
isotopes. Hydrogen has three well know isotopes called protium, deuterium, and
tritium.
Protium is by far the most
common – it has one
proton, one electron, and
no neutron. Deuterium,
also called heavy
hydrogen, is twice as
heavy as protium because
it has one proton, one
neutron, and one electron. Tritium is even heavier and is also radioactive. It is
rare on Earth.
Let’s look at an example of elemental notation for each of the three hydrogen
isotopes:
Each atom of hydrogen has one proton in its nucleus, so the atomic number of each
is "1" and that number can be found in the lower left corner. The mass number of
each of these atoms varies because they each have a different number of
neutrons. The first hydrogen has 2 neutrons in addition to the 1 proton in the
nucleus, for a total mass number of 3. The second atom has 1 neutron in addition
to the 1 proton in the nucleus, for a total mass number of 2. The third atom has no
neutrons, only 1 proton in its nucleus, for a mass number of 1.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Hydrogen is a good example to explain isotopes because it is easy to calculate, so it
is also a good example to describe how we come up with the atomic mass number.
Atomic mass is actually an average of all the isotopes of that element – so it is not
precise. If you were working on a critical experiment in subatomic chemistry it
might be worth your while to use the actual mass number for the correct isotope
of hydrogen you are using, but right now that level of accuracy is overkill.
Carbon is another good example – not because it is simpler to work with – but
because an isotope of carbon is how scientists came up with the unit for measuring
atomic mass. Remember that atomic mass is measured in amu’s or atomic mass
units? It turns out that the “u” or unit used for this measurement is based on an
isotope of carbon called carbon-12. Carbon-12 has a mass of exactly 12 units and
all other elemental isotopes are measured according to this isotope. It is the most
common of the stable carbon isotopes, but certainly not the most interesting.
Carbon-14 is a radioactive isotope of carbon, consisting of the following elemental
notation:
This notation states that the atomic number of Carbon is 6, the number of protons
is 6, and the number of neutrons is 8 – which gives us an atomic mass number of 14.
Carbon 14 is the basis of radiocarbon dating – which is a technique scientists use to
approximate the age of organic matter, such as archeological remnants.
It works like this: radiocarbon (carbon-14) is radioactive so it takes a very long
time to decay into nothingness. The half life for carbon-14 is about 5,700 years.
That means it takes about 5,700 years for one half of the isotope to decay.
Scientists use this half-life estimate of carbon -14 (and other radioactive
elements) to calculate how long an old organic object (which contains carbon) has
ceased to take in any new carbon – which is a scientific way to say “since it died.”
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
If an element has a charge on it – then it either has
extra electrons (- charge) or is missing electrons (+
charge), and the charge can also be depicted using
elemental notation. The notation to the right shows us
calcium, which has an atomic number of 20, and an
atomic mass of 40. That means it is not an isotope
because the number of protons equals the number of
neutrons.
In addition, this notation has a 2+ in
the upper right corner; this means it
has a net positive charge of 2. Since
an electron is negative – in order to
get a 2+ charge you must be missing
2 electrons or have 2 extra protons.
The only way to change the charge
of an element is to move electrons around because moving
protons around is not allowed! So we cannot actually have 2
extra protons! The way we find out how many electrons there
are in an element with a charge is to subtract a positive charge
from the number of electrons there should be, or to add a
negative charge to the number of electrons there should be.
For example – Ca has a positive charge of 2
(+2) and we know from the bottom left
number that the atomic number is 20 – that
means a normal atom of calcium has 20
protons and 20 electrons. We subtract 2
from 20 to get 18 total electrons. An
element which has more electrons than
protons or less electrons than protons is
called an ion.
Remember – any element with a charge must have extra or missing electrons since
you cannot move protons around.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Now let’s practice determining the number of protons, electrons, and neutrons in
an atom. Fill in the chart before going on.
Finding the number of protons is the easiest part – it is simply the atomic number
which is located on the bottom left of the notation.
The number of neutrons and protons is contained in the atomic mass number, which
is on the upper left, so all you have to do is subtract the protons from the atomic
mass number and you get the number of neutrons in the element.
Finding the number of electrons is not as easy as the other two, but it is still fairly
straight forward. Notice that bromine has a little negative sign in the upper right
corner – that means it has a negative charge. Now the ONLY way we can get an
overall negative charge on an element is to add electrons. So the first thing we
must do is determine how many electrons this element would have if there was no
charge.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
That’s easy because the number of electrons = the number of protons. So we begin
with 35 electrons, but we aren’t done. We must add an additional electron because
of the negative charge; this gives us an overall number of 36 electrons.
Remember that a negative charge means you have EXTRA electrons and a positive
charge means you are MISSING some electrons.
To find the number of electrons for Na (sodium) we must subtract from the
number of electrons we start with, so 11 -1 = 10 electrons.
To find the number of electrons for Sr (strontium) we must subtract 2 from our
original number of electrons because we had a +2 charge on the atom. This gives us
36.
And that’s pretty much it as far as basic atomic theory goes. You now know that
atoms are elements that contain subatomic particles. The subatomic particles give
the elements their properties and identity. You now also understand what an
isotope and an ion are, and you can figure out the basic characteristics of elements
by decoding their elemental notation. You’re really on your way to understanding
how chemistry works!
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Glossary
Alchemist – A practitioner of alchemy.
Alchemy – A medieval philosophy and early form of chemistry whose aims were the
transmutation of base metals into gold, the discovery of a cure for all diseases,
and the preparation of a potion that gives eternal youth. The imagined substance
capable of turning other metals into gold was called the philosophers' stone.
Antoine Lavoisier – French chemist known as the father of modern chemistry and
who discovered oxygen.
Atom – A unit of matter, the smallest unit of an element, having all the
characteristics of that element and consisting of a dense, central, positively
charged nucleus surrounded by a system of electrons.
Atomic Mass – The total mass of protons, neutrons and electrons in a single atom.
Atomic Mass Unit – A unit that is used for indicating mass on an atomic or
molecular scale.
Atomic Number – The number of protons found in the nucleus of an atom.
Atomic Theory – The physical theory of the structure, properties, and behavior of
the atom.
Atomos – The Greek word for divide or cut.
Carbon 12 – The more abundant of the two stable isotopes of the element carbon,
accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6
electrons.
Carbon 14 – A radioactive isotope of carbon with a nucleus containing 6 protons
and 8 neutrons.
Cathode Ray – A beam of electrons streaming from the negatively charged end of
a vacuum tube (the cathode) toward a positively charged plate (the anode).
Charge – A fundamental property of the elementary particles of which matter is
made that gives rise to attractive and repulsive forces.
Compound – A pure substance consisting of atoms or ions of two or more different
elements in definite proportions that cannot be separated by physical means.
Democritus – Greek philosopher who developed one of the first atomist theories of
the universe.
Deuterium – The hydrogen isotope which contains one proton and one neutron.
Electrical Charge – A form of charge, designated positive, negative, or zero, found
on the elementary particles that make up all known matter.
Electron – A negatively charged particle inside an atom and which resides outside
the nucleus.
Electron Cloud – An area inside the atom where electrons are likely to be found.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Element – A substance composed of atoms having an identical number of protons in
each nucleus. Elements cannot be reduced to simpler substances by normal
chemical means.
Elemental Notation – A shorthand way of writing information about a particular
type of element, isotope or atom.
Ernest Rutherford – Proved that most of the mass of an atom is due to the nucleus
and not the electron.
Ion - An atom or molecule in which the total number of electrons is not equal to
the total number of protons, giving it a net positive or negative electrical charge.
Isotope – Atoms that contain the same number of protons but a different number
of neutrons.
JJ Thompson – The scientist who discovered the electron using a cathode tube.
John Dalton – English chemist and physicist who formulated atomic theory.
Matter – Something that has mass and exists as a solid, liquid, gas, or plasma.
Molecule- A group of two or more atoms linked together by sharing electrons in a
chemical bond.
Neutron – An uncharged particle inside an atom and which resides inside the
nucleus.
Niels Bohr – Came up with the planetary model of the atom.
Nucleus – The positively charged central region of an atom, composed of protons
and neutrons and containing almost all of the mass of the atom.
Periodic Table – A tabular arrangement of the elements according to their atomic
numbers so that elements with similar properties are in the same column.
Planetary Model – A model of the atom where electrons orbit the nucleus like
planets orbit the sun.
Plum Pudding Model – Model of how electrons were positioned inside the atom.
Protium –The most common isotope of hydrogen, with one proton and no neutrons.
Proton – A positively charged particle inside an atom and which resides inside the
nucleus.
Radioactive – Process by which an atomic nucleus of an unstable atom loses energy
by emitting ionizing particles.
Radiocarbon Dating – a dating method that uses the naturally occurring
radioisotope carbon-14 to estimate the age of carbonaceous materials up to about
58,000 to 62,000 years.
Stoichiometry – Calculation of the quantities of reactants and products in a
chemical reaction.
Subatomic Particle – Any of various particles of matter that are smaller than a
hydrogen atom including protons, neutrons, and electrons.
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By J. Anne Huss
Tritium – A radioactive isotope of hydrogen which has one proton and two neutrons
in the nucleus.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Student Activities
Exercise One
Write the letter of the correct match next to each problem.
1. Atomic Theory a. A negatively charged particle inside an atom.
2.
Element
b. A table of elements which are arranged according to
atomic number.
3. Periodic Table c. The physical theory of the structure of the atom.
4.
Compound
d. A group of two or more atoms linked together by
chemical bonds.
5. Atom e. A unit of matter, the smallest unit of an element.
6.
Proton
f. A pure substance consisting of atoms or ions of two or
more different elements.
7.
Electron
g. Any of various particles of matter that are smaller than
an atom.
8. Neutron h. A positively charged particle inside an atom.
9.
Subatomic
Particle
i. An uncharged particle inside an atom.
10. Molecule j. A substance composed of atoms that are identical.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Exercise Two Write the letter of the correct match next to each problem.
1.
Nucleus
a. Calculation of the quantities of reactants and products in
a chemical reaction.
2.
Charge
b. English chemist and physicist who formulated atomic
theory.
3.
Matter
c. Greek philosopher who developed one of the first
atomist theories.
4. Atomos d. A pre-science chemistry.
5. Democritus e. Attractive and repulsive forces attached to matter.
6. Alchemist f. French chemist who discovered oxygen.
7. Alchemy g. A practitioner of alchemy.
8.
Antoine
Lavoisier
h. Something that has mass and exists as a solid, liquid,
gas, or plasma.
9. John Dalton i. The Greek word for divide or cut.
10. Stoichiometry j. The positively charged central mass of an atom.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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Exercise Three Write the letter of the correct match next to each problem.
1.
Electrical
Charge
a. Came up with the planetary model of the atom.
2.
Cathode Ray
b. The scientist who discovered the electron using a
cathode tube.
3. JJ Thompson c. The number of protons found in the nucleus of an atom.
4.
Plum Pudding
Model
d. Model of how electrons were positioned inside the atom.
5.
Ernest
Rutherford
e. An area inside the atom where electrons are likely to be
found.
6.
Niels Bohr
f. Proved that most of the mass of an atom is due to the
nucleus and not the electron.
7.
Planetary Model
g. A form of charge, designated positive, negative, or zero,
found on the elementary particles.
8.
Atomic Mass
Unit
h. A unit that is used for indicating mass on an atomic or
molecular scale.
9.
Atomic Number
i. A beam of electrons streaming from the negatively
charged end of a vacuum tube.
10.
Electron Cloud
j. A model of the atom where electrons orbit the nucleus
like planets orbit the sun.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
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By J. Anne Huss
Exercise Four Write the letter of the correct match next to each problem.
1.
Isotope
a. A radioactive isotope of carbon with a nucleus containing
6 protons and 8 neutrons.
2.
Atomic Mass
b. A radioactive isotope of hydrogen which has one proton
and two neutrons in the nucleus.
3.
Elemental
Notation
c. Process by which an atomic nucleus of an unstable atom
loses energy by emitting ionizing particles.
4.
Protium
d. The hydrogen isotope which contains one proton and one
neutron.
5.
Deuterium
e. An atom or molecule in which the total number of
electrons is not equal to the total number of protons.
6.
Tritium
f. The total mass of protons, neutrons and electrons in a
single atom.
7.
Radioactive
g. Atoms that contain the same number of protons but a
different number of neutrons.
8.
Carbon 12
h. The more abundant of the two stable isotopes of the
element carbon.
9.
Carbon 14
i. The most common isotope of hydrogen, with one proton
and no neutrons.
10.
Ion
j. A shorthand way of writing information about a particular
type of element, isotope or atom.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
24
By J. Anne Huss
Label the diagram of the atom using the word bank below.
Proton
Electron
Neutron
Nucleus
Electron Cloud
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
25
By J. Anne Huss
Study the elemental notation of this hypothetical potassium ion, and then fill in the
correct number for each subatomic particle.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
26
By J. Anne Huss
Parent Solutions
Exercise One Write the letter of the correct match next to each problem.
1. c Atomic Theory a. A negatively charged particle inside an atom.
2.
j
Element
b. A table of elements which are arranged according to
atomic number.
3. b Periodic Table c. The physical theory of the structure of the atom.
4.
f
Compound
d. A group of two or more atoms linked together by
chemical bonds.
5. e Atom e. A unit of matter, the smallest unit of an element.
6.
h
Proton
f. A pure substance consisting of atoms or ions of two or
more different elements.
7.
a
Electron
g. Any of various particles of matter that are smaller than
an atom.
8. i Neutron h. A positively charged particle inside an atom.
9.
g
Subatomic
Particle
i. An uncharged particle inside an atom.
10. d Molecule j. A substance composed of atoms that are identical.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
27
By J. Anne Huss
Exercise Two Write the letter of the correct match next to each problem.
1.
j
Nucleus
a. Calculation of the quantities of reactants and products in
a chemical reaction.
2.
e
Charge
b. English chemist and physicist who formulated atomic
theory.
3.
h
Matter
c. Greek philosopher who developed one of the first
atomist theories.
4. i Atomos d. A pre-science chemistry.
5. c Democritus e. Attractive and repulsive forces attached to matter.
6. g Alchemist f. French chemist who discovered oxygen.
7. d Alchemy g. A practitioner of alchemy.
8.
f
Antoine
Lavoisier
h. Something that has mass and exists as a solid, liquid,
gas, or plasma.
9. b John Dalton i. The Greek word for divide or cut.
10. a Stoichiometry j. The positively charged central mass of an atom.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
28
By J. Anne Huss
Exercise Three Write the letter of the correct match next to each problem.
1.
g
Electrical
Charge
a. Came up with the planetary model of the atom.
2.
i
Cathode Ray
b. The scientist who discovered the electron using a
cathode tube.
3. b JJ Thompson c. The number of protons found in the nucleus of an atom.
4.
d
Plum Pudding
Model
d. Model of how electrons were positioned inside the atom.
5.
f
Ernest
Rutherford
e. An area inside the atom where electrons are likely to be
found.
6.
a
Niels Bohr
f. Proved that most of the mass of an atom is due to the
nucleus and not the electron.
7.
j
Planetary Model
g. A form of charge, designated positive, negative, or zero,
found on the elementary particles.
8.
h
Atomic Mass
Unit
h. A unit that is used for indicating mass on an atomic or
molecular scale.
9.
c
Atomic Number
i. A beam of electrons streaming from the negatively
charged end of a vacuum tube.
10.
e
Electron Cloud
j. A model of the atom where electrons orbit the nucleus
like planets orbit the sun.
Exercise Four
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
29
By J. Anne Huss
Write the letter of the correct match next to each problem.
1.
g
Isotope
a. A radioactive isotope of carbon with a nucleus containing
6 protons and 8 neutrons.
2.
f
Atomic Mass
b. A radioactive isotope of hydrogen which has one proton
and two neutrons in the nucleus.
3.
j
Elemental
Notation
c. Process by which an atomic nucleus of an unstable atom
loses energy by emitting ionizing particles.
4.
i
Protium
d. The hydrogen isotope which contains one proton and one
neutron.
5.
d
Deuterium
e. An atom or molecule in which the total number of
electrons is not equal to the total number of protons.
6.
b
Tritium
f. The total mass of protons, neutrons and electrons in a
single atom.
7.
c
Radioactive
g. Atoms that contain the same number of protons but a
different number of neutrons.
8.
h
Carbon 12
h. The more abundant of the two stable isotopes of the
element carbon.
9.
a
Carbon 14
i. The most common isotope of hydrogen, with one proton
and no neutrons.
10.
e
Ion
j. A shorthand way of writing information about a particular
type of element, isotope or atom.
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
30
By J. Anne Huss
Label the diagram of the atom using the word bank below.
Proton
Electron
Neutron
Nucleus
Electron Cloud
Simple Schooling Atomic Theory ©2011 The Simple Homeschool
31
By J. Anne Huss
Study the elemental notation of this hypothetical potassium ion, and then fill in the
correct number for each subatomic particle.