Download Investigating Atoms and Atomic Theory

Kentucky Core Content




SC-08-1.1.1
Students will:
interpret models/representations of
elements;
classify elements based upon patterns in
their physical (e.g., density, boiling point,
solubility) and chemical (e.g., flammability,
reactivity) properties.
Core Content Cont.


SC-08-1.1.2
Students will understand that matter is made of
minute particles called atoms, and atoms are
composed of even smaller components. The
components of an atom have measurable
properties such as mass and electrical charge.
Each atom has a positively charged nucleus
surrounded by negatively charged electrons.
The electric force between the nucleus and the
electrons holds the atom together.
Core Content Cont.
SC-08-1.1.3
 Students will understand that the atom’s
nucleus is composed of protons and
neutrons that are much more massive
than electrons.

Investigating Atoms and Atomic Theory

Students should be able to:
Describe the particle theory of matter.
 Use the Bohr model to differentiate among the
three basic particles in the atom (proton,
neutron, and electron) and their charges,
relative masses, and locations.
 Compare the Bohr atomic model to the
electron cloud model with respect to their
ability to represent accurately the structure of
the atom.

Why do physicists study
particles?
Physicists study particles
because everything is made
of them, including us! People
have been trying to
understand what the Universe
is made of forever. One of the
earliest theories said that
everything could be built from
just four elements, Earth, Air,
Fire and Water. This was a
great scientific theory
because it was simple. But it
had one big drawback: it was
wrong. WHY?
Atomos: Not to Be Cut
The History of Atomic Theory
Atomic Models

This model of the
atom may look
familiar to you. This is
the Bohr model. In
this model, the
nucleus is orbited by
electrons, which are
in different energy
levels.

A model uses familiar ideas to
explain unfamiliar facts
observed in nature.

A model can be changed as
new information is collected.
 The
atomic
model has
changed
throughout the
centuries,
starting in 400
BC, when it
looked like a
billiard ball →
Who are these men?
In this lesson, we’ll learn
about the men whose quests
for knowledge about the
fundamental nature of the
universe helped define our
views.
Democritus

This is the Greek
philosopher Democritus
who began the search for
a description of matter
more than 2400 years
ago.
 He asked: Could
matter be divided into
smaller and smaller
pieces forever, or was
there a limit to the
number of times a
piece of matter could
be divided?
400 BC
Atomos



His theory: Matter could
not be divided into
smaller and smaller
pieces forever, eventually
the smallest possible
piece would be obtained.
This piece would be
indivisible.
He named the smallest
piece of matter “atomos,”
meaning “not to be cut.”
Atomos


To Democritus, atoms
were small, hard
particles that were all
made of the same
material but were
different shapes and
sizes.
Atoms were infinite in
number, always
moving and capable
of joining together.
This theory was ignored and
forgotten for more than 2000
years!

The eminent
philosophers
of the time,
Aristotle and
Plato, had a
more
respected,
(and
ultimately
wrong)
theory.
Aristotle and Plato favored the earth, fire, air
and water approach to the nature of matter.
Their ideas held sway because of their
eminence as philosophers. The atomos idea
was buried for approximately 2000 years.
Dalton’s Model

In the early 1800s,
the English
Chemist John
Dalton performed a
number of
experiments that
eventually led to
the acceptance of
the idea of atoms.
Dalton’s Theory




He deduced that all
elements are composed of
atoms. Atoms are
indivisible and
indestructible particles.
Atoms of the same element
are exactly alike.
Atoms of different elements
are different.
Compounds are formed by
the joining of atoms of two
or more elements.
.
 This
theory
became one
of the
foundations
of modern
chemistry.
Thomson’s Plum Pudding
Model
 In
1897, the
English scientist
J.J. Thomson
provided the first
hint that an atom
is made of even
smaller particles.
Thomson Model
He proposed a
model of the atom
that is sometimes
called the “Plum
Pudding” model.
 Atoms were made
from a positively
charged substance
with negatively
charged electrons
scattered about,
like raisins in a
pudding.

 Thomson
Thomson Model
studied
the passage of
an electric
current through a
gas.
 As the current
passed through
the gas, it gave
off rays of
negatively
charged
particles.
Thomson Model
 This
surprised
Thomson,
because the
atoms of the gas
were uncharged.
Where had the
negative charges
come from?
Where did
they come
from?
Thomson concluded that the
negative charges came from within
the atom.
A particle smaller than an atom had
to exist.
The atom was divisible!
Thomson called the negatively
charged “corpuscles,” today known
as electrons.
Since the gas was known to be
neutral, having no charge, he
reasoned that there must be
positively charged particles in the
atom.
But he could never find them.
Rutherford’s Gold Foil
Experiment

In 1908, the
English physicist
Ernest Rutherford
was hard at work
on an experiment
that seemed to
have little to do
with unraveling the
mysteries of the
atomic structure.
 Rutherford’s
experiment Involved
firing a stream of tiny positively
charged particles at a thin sheet of
gold foil (2000 atoms thick)


Most of the positively
charged “bullets” passed
right through the gold
atoms in the sheet of
gold foil without changing
course at all.
Some of the positively
charged “bullets,”
however, did bounce
away from the gold sheet
as if they had hit
something solid. He
knew that positive
charges repel positive
charges.

http://chemmovies.unl.edu/ChemAnime/R
UTHERFD/RUTHERFD.html




This could only mean that the gold atoms in the
sheet were mostly open space. Atoms were not
a pudding filled with a positively charged
material.
Rutherford concluded that an atom had a small,
dense, positively charged center that repelled
his positively charged “bullets.”
He called the center of the atom the “nucleus”
The nucleus is tiny compared to the atom as a
whole.
Rutherford

Rutherford reasoned
that all of an atom’s
positively charged
particles were
contained in the
nucleus. The
negatively charged
particles were
scattered outside the
nucleus around the
atom’s edge.
Bohr Model
 In
1913, the
Danish scientist
Niels Bohr
proposed an
improvement. In
his model, he
placed each
electron in a
specific energy
level.
Bohr Model

According to
Bohr’s atomic
model, electrons
move in definite
orbits around the
nucleus, much like
planets circle the
sun. These orbits,
or energy levels,
are located at
certain distances
from the nucleus.
Wave Model
The Wave Model
Today’s atomic
model is based on
the principles of
wave mechanics.
 According to the
theory of wave
mechanics,
electrons do not
move about an
atom in a definite
path, like the
planets around the
sun.

The Wave Model


In fact, it is impossible to determine the exact
location of an electron. The probable location of
an electron is based on how much energy the
electron has.
According to the modern atomic model, an atom
has a small positively charged nucleus
surrounded by a large region in which there are
enough electrons to make an atom neutral.
Electron Cloud:




A space in which
electrons are likely to be
found.
Electrons whirl about the
nucleus billions of times
in one second
They are not moving
around in random
patterns.
Location of electrons
depends upon how much
energy the electron has.
Electron Cloud:



Depending on their energy they are locked into a
certain area in the cloud.
Electrons with the lowest energy are found in
the energy level closest to the nucleus
Electrons with the highest energy are found
in the outermost energy levels, farther from
the nucleus.
Indivisible Electron
Greek
X
Dalton
X
Nucleus
Thomson
X
Rutherford
X
X
Bohr
X
X
Wave
X
X
Orbit
Electron
Cloud
X
X
List 3 key points
from today’s
lesson on atomic
theory history.
Journal

Compare and contrast physical and
chemical changes in matter.
You may use any graphic organizer you
wish to complete this journal.
Atomic
Structure
Core Content for Assessment

SC-08-1.1.3


Students will understand that the atom’s nucleus is
composed of protons and neutrons that are much more
massive than electrons.
SC-08-1.1.2

Students will understand that matter is made of minute
particles called atoms, and atoms are composed of even
smaller components. The components of an atom have
measurable properties such as mass and electrical charge.
Each atom has a positively charged nucleus surrounded by
negatively charged electrons. The electric force between the
nucleus and the electrons holds the atom together.
Structure of an atom
(page 256 in Sciencesaurus)

Nucleus – The core of an atom. Contains
protons and neutrons.

Protons – Positively (+) charged particles
found in the nucleus of an atom.

Neutrons – Neutrally charged particles found
in the nucleus of an atom.

Electrons – Negatively (-) charged particles
found outside the nucleus of an atom.
Structure of an atom

Valence electron – the fartheset away or most
loosely held electrons which help determine
how elements bond.

Electron Dot Diagram – A diagram in which
each dot represents one electron in the outer
valence “shell”. (pg 268 in Sciencesaurus)

Isotopes – Atoms of the same element that
have different number of neutrons (eg.
Carbon)
1st Verse:
They’re tiny and they’re
teeny,
Much smaller than a beany,
They never can be seeny,
The Atoms Family.
Chorus
3rd Verse:
Neutrons can be found,
Where protons hang
around;
Electrons they surround
The Atoms Family.
Chorus
2nd Verse:
Together they make gases,
And liquids like molasses,
And all the solid masses,
The Atoms Family
Chorus
Chorus:
They are so small.
(Snap, snap)
They’re round like a ball.
(Snap, snap)
They make up the air.
They’re everywhere.
Can’t see them at all.
(Snap, snap)
They’re tiny and they’re
teeny,
Much smaller than a
beany,
They never can be seeny,
The Atoms Family.
They are so small.
(Snap, snap)
They’re round like a ball.
(Snap, snap)
They make up the air.
They’re everywhere.
Can’t see them at all.
(Snap, snap)
Together they make gases,
And liquids like molasses,
And all the solid masses,
The Atoms Family
They are so small.
(Snap, snap)
They’re round like a ball.
(Snap, snap)
They make up the air.
They’re everywhere.
Can’t see them at all.
(Snap, snap)
Neutrons can be found,
Where protons hang around;
Electrons they surround
The Atoms Family.
Journal
What is the name of this atom model and
who was the scientist that created it?
Reviewing Matter

Three principal states of matter
Solid
 Liquid
 Gas

States of matter
Solid: molecules are tightly packed together;
definite shape and volume
 Liquid: molecules are able to move around, but
are still bonded; no definite shape, but definite
volume


Viscosity: the resistance of a liquid to flowing.
 High
viscosity flows slowly
 Low viscosity flows quickly

Gas: molecules are spread apart, filling the
space available; no definite shape or volume
Characteristics of matter
Boiling point (vaporization): the temperature at
which a liquid changes to a gas
 Melting point: the temperature at which a solid
changes to a liquid
 Condensation point: the temperature at which a
gas turns to a liquid (the same temperature as
the boiling point)
 Freezing point: the temperature at which a
liquid changes to a solid (the same temperature
as the melting point)

Changes in Matter
 Physical
change: alters the form of a
substance, but not its identity
 Examples:
mixing salt and water, freezing
water
 Chemical
change: substances combine
or break apart to form new substances
 Examples:
burning wood, heating sugar to
make caramel
Types of Matter
 Mixtures:
two or more substances that
are in the same place but are not
chemically combined
 Examples:
 Pure
Kool-aid, sea water
substances: made of only one kind
of matter and has definite properties.
Pure Substances
 Elements:
a substance that cannot be
broken down into other substances by
chemical or physical means
 Examples:
iron, copper, aluminum
 Compounds:
a substance made of two or
more elements that are chemically
combined
 Examples:
sugar, salt
Clean sheet of paper
 Put
your name on the paper
 Number your page 1-22
 On the next slide, you will see a
list of items, place a “P” next to
the number if the change is
physical
 Place a “C” next to the number if
the change is chemical
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Glass breaking
Hammering wood together to build a
playhouse
A rusting bicycle
Melting butter for popcorn
Glassblower creating sculptures out of glass
Freezing chocolate-covered bananas
Separating sand from gravel
Spoiling food
Burning toast
Making salt water to gargle for a sore throat
Mixing lemonade powder into water
12.Cream
being whipped
13.Water evaporating from a pond
14.Cutting grass
15.Burning leaves
16.Humidifier putting moisture into the air
17.Corroding metal
18.Bleaching your hair
19.Fireworks exploding
20.Squeezing oranges to get orange juice
21.Frying an egg
22.Pouring milk on your oatmeal
Journal
Page 79 in book
1. Write a conclusion for your
lab yesterday about
whether or not your
substances were changed
physically or chemically.
Elements and the Periodic
Table
(page 265 in Sciencesaurus)
Core Content for
Assessment
SC-08-1.1.1
 Students will:
 interpret models/representations of elements;
 classify elements based upon patterns in their physical (e.g.,
density, boiling point, solubility) and chemical (e.g.,
flammability, reactivity) properties.
 Models enhance understanding that an element is composed of
a single type of atom. Organization/interpretation of data
illustrates that when elements are listed according to the
number of protons, repeating patterns of physical (e.g., density,
boiling point, solubility) and chemical properties (e.g.,
flammability, reactivity), can be used to identify families of
elements with similar properties.
DOK 2
Why is the Periodic Table
important to me?



The periodic table is
the most useful tool to
a chemist.
You get to use it on
every test.
It organizes lots of
information about all
the known elements.
Pre-Periodic Table Chemistry …





…was a mess!!!
No organization of
elements.
Imagine going to a
grocery store with no
organization!!
Difficult to find
information.
Chemistry didn’t make
sense.
Dmitri Mendeleev: Father of the
Table


HOW HIS
WORKED…
Put elements in rows
by increasing atomic
mass.
Put elements in
columns by the way
they reacted.


SOME
PROBLEMS…
He left blank spaces
for what he said were
undiscovered
elements. (Turned
out he was right!)
He broke the pattern
of increasing atomic
mass to keep similar
reacting elements
together.
The Current Periodic Table
Mendeleev wasn’t too far off.
 Now the elements are put in rows by

ATOMIC
NUMBER!!
increasing
The horizontal rows are called periods and
are labeled from 1 to 7.
 The vertical columns are called groups are
labeled from 1 to 18.

Groups




Vertical columns of elements
in the periodic table.
Also known as Families.
Families may be one column,
or several columns put
together.
The elements in each group or
family, have similar
characteristics.
Families have names rather
than numbers. (Just like your
family has a common last
name.)
Groups…Here’s Where the
Periodic Table Gets Useful!!
 Elements
in
the same
group have
similar
chemical and
physical
properties!!

(Mendeleev did that on
purpose.)
Why??
• They have the same
number of valence
electrons.
• They will form the
same kinds of ions.
Hydrogen




Hydrogen belongs to a
family of its own.
Hydrogen is a diatomic,
reactive gas.
Hydrogen was involved in
the explosion of the
Hindenberg.
Hydrogen is promising as
an alternative fuel source
for automobiles
Alkali Metals



1st column on the
periodic table (Group
1) not including
hydrogen.
Very reactive metals,
always combined with
something else in
nature (like in salt).
Soft enough to cut
with a butter knife
Alkaline Earth Metals



Second column on
the periodic table.
(Group 2)
Reactive metals that
are always combined
with nonmetals in
nature.
Several of these
elements are
important mineral
nutrients (such as Mg
and Ca
Transition Metals





Elements in groups
3-12
Less reactive harder
metals
Includes metals
used in jewelry and
construction.
Metals used “as
metal.”
Conduct heat &
electricity. (ductile)
Synthetic Elements
Man-made –
elements greater
than atomic #92
 Example promethium (61)
 Some radioactive
 Used in medical
diagnosis &
treatment

Nonmetals


Some elements in groups 13-16 &
all the elements of group 17 & 18
& hydrogen.
Nonmetals have a sub groups
called:




Hydrogen
Other Nonmetals
 Chalogens (Stinky family)
 Semiconductors
Halogens
Noble Gases
Oxygen Family or Chalcogens



Oxygen, Sulfur
Oxygen is necessary
for respiration.
Many things that
stink, contain sulfur
(rotten eggs, garlic,
skunks, etc.)
Semiconductors/Metalloids

Element – Carbon, Silicon,
Germainium
Usually found as graphite
(lead used in pencils)
 Diamonds
 Major component of living
and nonliving organisms
 Silicon is the most abundant
element compound in the
Earth’s crust – used in
computers, find it in sand

Nitrogen Family





Elements in group 15
Nitrogen makes up over
¾ of the atmosphere.
Nitrogen and
phosphorus are both
important in living
things.
Most of the world’s
nitrogen is not available
to living things.
The red stuff on the tip
of matches is
phosphorus.
Halogens




Elements in group 17
Very reactive, volatile,
diatomic, nonmetals
Always found
combined with other
element in nature .
Used as disinfectants
and to strengthen
teeth.
The Noble Gases
The Noble Gases






Elements in group 18
VERY unreactive, monatomic
gases (inert)
Used in lighted “neon” signs
Used in blimps to fix the
Hindenberg problem.
Have a full valence shell.
Exists as single atoms not
molecules.
The Atoms Family Story
In the center of Matterville, there is a
place called the Nucleus Arcade,
where two members of the Atoms
Family like to hang out. Perky Patty
Proton, like her sisters, is quite large
with a huge smile and eyes that
sparkle (+). Patty is always happy
and has a very positive personality.
Nerdy Nelda Neutron is large like
Patty, but she has a boring, flat
mouth and eyes with zero expression
(o). Her family is very apathetic and
neutral about everything.
Patty,
Nelda, and their sisters spend all their
time at the arcade.
Name:
Patty Proton
Description:
Positive
Favorite Activity:
Hanging out at the Nucleus
Arcade
Name:
Nelda Neutron
Description:
Neutral
Favorite Activity:
Hanging out at the Nucleus
Arcade
Around the Nucleus Arcade, you
will find a series of roadways that
are used by another member of the
Atoms Family, Enraged Elliott
Electron. Elliott races madly
around the Arcade on his bright
red
chrome-plated
HarleyDavidson. He rides so fast that no
one can be sure where he is at any
time. Elliott is much smaller than
Patty and Nelda and he is always
angry because these bigger
relatives will not let him in the
Arcade. He has a frown on his
face, eyes that are squinted with
anger, and a very negative (-)
attitude.
Name:
Elliott Electron
Description:
Negative
Favorite Activity:
Racing around the arcade
The morale of Matterville is stable as long as each negative
Electron brother is balanced out by one positive Proton sister.
The number of residents in Matterville depends on the Proton
and Neutron families.
Challenge: What would happen to the morale of Matterville if
one Elliott Electron was kidnapped?
The first energy street can only
hold only two Electron brothers.
The second and third energy
streets, called the Energy Freeway,
can hold 8 brothers. The fourth
energy street, called the Energy
Superhighway, can hold 18 of the
brothers.
Energy Freeway
Can hold 8
electrons
Energy Street
Can hold 2
electrons
Energy
Superhighway Can
hold 18 electrons
Energy
Freeway Can
hold 8
electrons
Nucleus Arcade
Contains protons &
neutrons
Valence Electrons

Electrons that are involved in transfer or
sharing.

The number of valence electrons an
element has increases from left to right
across a period.
The Atoms Family - Atomic Math
Challenge
Atomic Number
Symbol
Name
Atomic Mass
Atomic number equals the number ofprotons
____________
Atomic mass equals the number of ______________
+ __________
neutrons
protons
Assignment: Finish the rest of the worksheet and
turn it in to your teacher.
“Electron Cloud”

Electrons are arranged around the
Nucleus in SHELLS. For simplicity they
can be thought of like mini-planets orbiting
a central sun, but it is closer to the truth to
think of them as "clouds" of electric charge
around the Nucleus.
Electron Dot Diagrams
Examine the Electron Dot Diagram above – write at
least 3 observations about the periodic table’s
arrangement and how the arrangement compares
to the number of dots it has beside it. Use the
sciencesaurus book to help you write your
observations page 265. Read page 268 – write 2
facts
How to write and Electron Dot Diagram
1.
2.
3.
Write the symbol of the element.
(Each side of the letter represents
an electron orbital.)
Find the # of electrons in the
valence shell (the outermost
shell).
The dots representing the
electrons in the valence shell are
placed around the symbol
beginning with the right side of the
letter.
C