HISTORY OF THE ATOM
460 BC
Democritus develops the idea of atoms
he pounded up materials in his pestle and
mortar until he had reduced them to smaller
and smaller particles which he called
ATOMA
(greek for indivisible)
HISTORY OF THE ATOM
1808
John Dalton
suggested that all matter was made up of
tiny spheres that were able to bounce around
with perfect elasticity and called them
ATOMS
HISTORY OF THE ATOM
1898
Joseph John Thompson
found that atoms could sometimes eject a far
smaller negative particle which he called an
ELECTRON
HISTORY OF THE ATOM
1904
Thompson develops the idea that an atom was made up of
electrons scattered unevenly within an elastic sphere surrounded
by a soup of positive charge to balance the electron's charge
like plums surrounded by pudding.
PLUM PUDDING
MODEL
HISTORY OF THE ATOM
1910
Ernest Rutherford
oversaw Geiger and Marsden carrying out his
famous experiment.
they fired Helium nuclei at a piece of gold foil
which was only a few atoms thick.
they found that although most of them
passed through. About 1 in 10,000 hit
HISTORY OF THE ATOM
helium nuclei
gold foil
helium nuclei
They found that while most of the helium nuclei passed
through the foil, a small number were deflected and, to their
surprise, some helium nuclei bounced straight back.
HISTORY OF THE ATOM
Rutherford’s new evidence allowed him to propose a more
detailed model with a central nucleus.
He suggested that the positive charge was all in a central
nucleus. With this holding the electrons in place by electrical
attraction
However, this was not the end of the story.
HISTORY OF THE ATOM
1913
Niels Bohr
studied under Rutherford at the Victoria
University in Manchester.
Bohr refined Rutherford's idea by adding
that the electrons were in orbits. Rather
like planets orbiting the sun. With each
orbit only able to contain a set number of
electrons.
Bohr’s Atom
electrons in orbits
nucleus
HELIUM ATOM
Shell
proton
+
-
N
N
+
electron
What do these particles consist of?
-
neutron
ATOMIC STRUCTURE
Particle
Charge
Mass
proton
+ ve charge
1
neutron
No charge
1
electron
-ve charge
nil
The Atoms Family was created by Kathleen Crawford, 1994
Presentation developed by Tracy Trimpe, 2006, http://sciencespot.net/
The Atoms Family Story
In the center of Matterville, there
is a place called the Nucleus
Name:
Arcade, where two members of
Patty Proton
the Atoms Family like to hang
Description:
out. Perky Patty Proton, like
Positive
her sisters, is quite large with a
Favorite Activity:
huge smile and eyes that sparkle
Hanging out at the Nucleus
(+). Patty is always happy and
Arcade
has a very positive personality.
Nerdy Nelda Neutron is large Name:
like Patty, but she has a boring, Nelda Neutron
flat mouth and eyes with zero
Description:
expression (o). Her family is very
Neutral
apathetic and neutral about
Favorite Activity:
everything. Patty, Nelda, and Hanging out at the Nucleus
their sisters spend all their time at Arcade
the 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 chromeplated Harley-Davidson. 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 first energy street can only hold
only two Electron brothers. The
second energy street, called the
Energy Freeway, can hold 8
brothers. The third 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 8 electrons
Nucleus Arcade
Contains protons &
neutrons
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?
Challenge 2: What would happen to the morale of Matterville if one
Elliott Electron moved to Matterville?
Subatomic Particles
1.
2.
3.
4.
5.
6.
7.
8.
What are the subatomic particles of an atom?
Where are the protons located in the atom?
What electrical charge do protons have?
Where are the neutrons located?
What electrical charge do the neutrons have?
Where are the electrons located in an atom?
What electrical charge do electrons have?
How does the number of protons affect the
properties of an atom?
Models of Atoms
Dish #
Protons Neutrons Electrons Atomic Elem
ent
(+)
(0)
(-)
#
Atom
ic
mass
ATOMIC STRUCTURE
He
2
4
Atomic number
the number of protons in an atom
Atomic mass
the number of protons and
neutrons in an atom
number of electrons = number of protons
The Atoms Family - Atomic Math
Challenge
Atomic Number
Symbol
Name
Atomic Mass
electrons
protons
Atomic number equals the number of _________or_______________.
neutrons
protons + _______________.
Atomic mass equals the number of ___________
30
8
16
65
8
30
8
8
3
7
3
35
4
30
3
5
35
28
11
80
14
14
5
6
45
14
5
35
14
35
Drawing Atomic Structures
PROTONS (P+) + NEUTRONS = ATOMIC MASS
For example: p + n = atomic mass
An element with atomic number 17, how many
neutrons does it contain?
If p + n = am, then 17 + n = 35
n = 35 – 17
n = 18
An element with atomic number 17, how many neutrons does it
contain?
If p + n = am, then 17 + n = 35
en = 35 – 17
e3rd
P= 3 What is n?
n = 18
e- e-
If p + n = am
3+n=7
n=7–3
N=4
----------------------------------p = 80
80 + n = 201
n = 201 – 80
n = 121
---------------------------------p = 82, 82 + n = 207
n = 207 – 82
n = 125
2nd
ee-
e-
1st
ee-
e-
e-
eee-
e-
e- e-
e-
Valence Electrons
• Each energy level can
hold a specific
number of electrons.
• For example. The 1st
energy level can hold
2 electrons.
e• The 2nd and 3rd
eenergy levels can
hold up to 8 electrons
each.
3rd
e-
ee- e-
2nd
ee-
e-
1st
ee-
eee-
e-
e- e-
e-
Atomice- Structure:
eeee-
ee-
e-
4th shelle-
ee-
e-
e-
2nd
ee-
ee-
p+
p+ p+ n
p+p+ p+ n
p+
p+ p+ p+ n
p+ n
p+p+
p+ p+ n
p+p+
p+
ee-
e3rd
Shell,
e- or
Orbit
e-
e-
nn
n
n nn n 1st orbit
n nn
nn
n
e-
e-
e-
e-
e-
eee-
eee-
Nucleus= MOST of the MASS is located here!
REMEMBER PROTONS + NEUTRONS = ATOMIC MASS
e-
e-
3rd
ee-
2nd
e-
1st
e-
e-
ee-
e-
e-
e-
e-
e-
eee-
e-
ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or
Shells around the nucleus of an atom.
•
first shell
a maximum of 2 electrons
•
second shell
a maximum of 8 electrons
•
third shell
a maximum of 8 electrons
SUMMARY
1. The Atomic Number of an atom = number of
protons in the nucleus.
2. The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
3.
The number of Protons = Number of Electrons.
4.
Electrons orbit the nucleus in shells.
5.
Each shell can only carry a set number of electrons.