simple schooling atomic theory ©2011 the simple...

Simple Schooling Atomic Theory ©2011 The Simple Homeschool

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By J. Anne Huss


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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.


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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.


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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


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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.


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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.


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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”

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::100%25::100%25::/sites/dl/free/0072512644/117354/01_Cathode_Ray_Tube.swf::Cathode%20Ray%20Tube


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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.

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf


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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.


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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.


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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:


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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.


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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.”


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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.


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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.


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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!


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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.


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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.


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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.


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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.


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By J. Anne Huss

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.


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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



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By J. Anne Huss

Label the diagram of the atom using the word bank below.

Proton

Electron

Neutron

Nucleus

Electron Cloud


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By J. Anne Huss

Study the elemental notation of this hypothetical potassium ion, and then fill in the

correct number for each subatomic particle.


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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.


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.


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


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



30

By J. Anne Huss

Label the diagram of the atom using the word bank below.

Proton

Electron

Neutron

Nucleus

Electron Cloud


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.

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