# The Building Blocks of Matter Atoms

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```					The Building Blocks of Matter:
Atoms

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++ +
-       + + +        -
+  +
-

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Note-Taking Instructions
• As 8th graders, you will be responsible for
organizing your own notes this year. No
• To assist you in your note-taking, I have
highlighted the areas of greatest concern
by changing the font color to red (just
like last year)
• You may, however, write as much
information as you need for your notes.
Just make sure you write everything that
you see in red!
Matter
• Anything that has mass and takes up
space (volume)
– Examples:
•   A brick has mass and takes up space
•   A desk has mass and takes up space
•   A pencil has mass and takes up space
•   Air has mass and takes up space

All of the above examples are considered matter because
they have mass and take up space. Can you think of anything
that would not be considered matter?
Atoms
• Smallest possible unit
into which matter can
be divided, while still
-           maintaining its
properties.
• Made up of:
-   +             – protons +

+++    -
– neutrons
– electrons   -

• The solar system is
-           commonly used as an
analogy to describe the
structure of an atom
Atoms are so small that…
•   it would take a stack of about
50,000 aluminum atoms to equal
the thickness of a sheet of
aluminum foil from your kitchen.
•   if you could enlarge a penny until
www.deckersfoods.com

it was as wide as the US, each
of its atoms would be only about
3 cm in diameter – about the
size of a ping-pong ball
•   a human hair is about 1 million
carbon atoms wide.                C-C-C-C-C-… + 999,995 more
•   a typical human cell contains
roughly 1 trillion atoms.                                     1 trillion atoms 
•   a speck of dust might contain
3x1012 (3 trillion) atoms.      .
Is made of approximately 3 trillion atoms
•   it would take you around 500
years to count the number of
atoms in a grain of salt.
Just one of these grains
Let’s Experiment
In order to try to gain an idea of how
small an atom really is, you will complete
the following activity.
1. Cut a strip of 11 in. paper in half.
2. Discard one half.
3. Cut the remaining piece in half.
4. Continue cutting and discarding the strips as
many times as you can.
5. Make all cuts parallel to the first one. When
the width gets longer than the length, you
may cut off the excess, but that does not
count as a cut.
Results
• How many cuts were you able to
make?
• Do you think you could keep cutting
the paper forever? Why or why not?

You would have to cut the paper in
half around thirty-one (31) times to
get to the size of any atom.
http://www.miamisci.org/af/sln/phantom/papercutting.html
Protons (+)
• Positively charged            -           -
particles                           -
• Help make up the          -
++ +
+ + +       -
nucleus of the atom                + +
• Help identify the atom              -
(could be considered an       -           -
atom’s DNA)
• Equal to the atomic
number of the atom
• Contribute to the
atomic mass
• Equal to the number of        +
electrons
Neutrons
-           -
-
• Neutral particles;
-
++ +
+ + +       -         have no electric
+ +                  charge
-
-           -           • Help make up the
nucleus of the
atom
• Contribute to the
atomic mass
Electrons (-)
• Negatively charged particles
-           -
• Found outside the nucleus of
the atom, in the electron                    -
orbits/levels; each orbit/level             ++ +
can hold a maximum number          -       + + +       -
of electrons ( 1st = 2, 2nd = 8,            + +
3rd = 8 or 18, etc…)                         -
• Move so rapidly around the             -           -
nucleus that they create an
electron cloud
• Mass is insignificant when
compared to protons and
neutrons
• Equal to the number of
protons
-
• Involved in the formation of
chemical bonds
Hydrogen (H) Atom
• Notice the one electron in the first orbital

+ =1
-                       How many
=0                                               more
electrons
can fit in
-   =1
+                         the 1st
orbital/
level?

Even though there are no neutrons present,
Hydrogen is still considered an atom
Oxygen (O) Atom
• Notice the two electrons in the first orbital/level
and the six in the second

+ =8
-               -           How many
=8                                        more
-                   electrons
can fit in
-   =8
++ +                   the 2nd
+ + +                   orbital/
-                       -         level?
+  +
-

-              -
Sodium (Na) Atom
• Notice the two electrons in the first orbital/level,
eight in the second, and one in the third

+ = 11                   -
-                   -           How many
= 12                                           more
-                      electrons
can fit in
-   = 11
++ +                       the 3rd
-        + + +              -   -    orbital/
level?
+  +
-
-               -
-
The Atom’s “Center”

• Protons and neutrons are grouped together to
form the “center” or nucleus of an atom.
Notice that the electrons are not apart of the nucleus

-
-
+
+ +
-
QUARKS
• Particles that make up protons and neutrons

Notice the                                            Notice the
smaller                                               smaller
particles                                             particles
that make                                             that make
up this
neutron
after you
+               up this
proton
after you
take a                                                take a
closer look.                                          closer look.

What do you notice about the number
of quarks in the neutron and proton?
Sub-Atomic Particles
Weight Comparison
(protons, neutrons, electrons)

Neutron = 1.6749286 x10 -27 kg
Proton = 1.6726231 x10 -27 kg
Electron = 9.1093897 x10 -31 kg

-                                          -
- -
- - -
- - - - -
- - - - - - -
- -
- - -
- - - - -
- - - - - - -
+
1839 electrons = 1 neutron                 1836 electrons = 1 proton

How do you think the mass of a neutron
compares to that of a proton?
+
1 neutron ≈ 1 proton
Sub-atomic Particles
Size Comparison
(protons, neutrons, electrons, & quarks)

Size in       Size in                     -                 -
atoms         meters
(m)                                     -
Atom           1           10-10
++ +
Nucleus       __1__          10-14                               + + +
10,000                             -                           -
Proton or    ___1___         10-15                                +  +
100,000
Neutron

Electron    _____1____       10-18                                   -
100,000,000
or Quark                   (at largest)

-                -
Atomic Number
• The number of protons in the nucleus of an atom

-
What would
be the atomic
number of this
+          -
atom?
-      ++
Mass Number
•   The total number of protons and neutrons in an atom’s nucleus
•   Expressed in Atomic Mass Units (amu)
– Each proton or neutron has a mass of 1 amu

What would be the mass
number of this atom?                     -

+    3
4
+            -
3 protons + 4 neutrons =
a mass number of 7 amu                  ++
Why did we not account for the        -
electrons when calculating the
mass number?
How to Obtain the Number of Sub-Atomic Particles in
an Atom Using a Periodic Table
-                             -
-

+    = 8                            ++ +
-             + + +                      -
= 8
+  +
-   = 8
-
-                         -

Protons                        Neutrons                          Electrons
+                                                                 -

Equal to the atomic #          Equal to the atomic mass              Equal to the # of
on the Periodic Table          (rounded to a whole #)                    protons
minus the # of protons

Example: Determine the # of protons, neutrons, and electrons in an atom of oxygen.
Protons = 8 (Atomic #)    Neutrons = 8 (Rounded atomic mass minus atomic #)        Electrons = 8 (# of P)
Neutron Calculations = 16 (P + N) – 8 (P) = 8 N
How to Obtain the Number of Sub-Atomic Particles in
an Ion Using a Periodic Table
-                     -
-
Notice
how two                       2-                      +    = 8           -                  ++ +
electrons                                                                                  + + +
have been                                                   = 8
-
gained by
the atom,                                                     8
= 10
+   +
-
thus
resulting in                                                                     -                   -
an ion                                                                                                        -

Protons                         Neutrons
Electrons
+                                                                         -

Equal to the # of protons plus the # in
Equal to the atomic #             Equal to the atomic mass          the upper right corner if followed by a
on the Periodic Table             (rounded to a whole #)             (-) OR minus the # in the upper right
minus the # of protons                  corner if followed by a (+)

Example: Determine the # of protons, neutrons, and electrons in the oxygen ion O²¯.
Protons = 8 (Atomic #)             Neutrons = 8 (Rounded atomic mass minus atomic #)              Electrons = 10
Neutron Calculations = 16 (P + N) – 8 (P) = 8 N                            Electron Calculations = 8 (e) + 2 (e) = 10
Building Atoms
Using an expo marker and your desk, draw the
following atoms, and determine their atomic and
mass numbers. Be ready to share your drawings with
the class.

Atoms     Protons   +   Neutrons   Electrons   -
Carbon          6              6         6
Beryllium       4              5         4
Oxygen          8              8         8
Lithium         3              4         3
Sodium          11            12         11
FORCES IN THE ATOM

• Gravitational Force
• Electromagnetic Force
• Strong Force
• Weak Force
Gravitational Force
• The force of
attraction of
objects due to
their masses
• The amount of
gravity between
objects depends on
their masses and
the distance
between them

Do you think this force plays a significant
role in holding the atom together?
Electromagnetic Force
• The force that                          + +
results from the
repulsion of like           -                             +
charges and the
attraction of                             - -
opposites
Notice how the
• The force that holds            particles with the same
the electrons around            charge move apart and
the particles with
the nucleus                       different charges
move together.

Why are neutrons not
pictured above?
Strong Force
• The force that      Notice how the electromagnetic
force causes the protons to repel
holds the atomic   each other but, the strong force
holds them together.
nucleus together
• The force that
counteracts the                   +
electromagnetic               +        +
force                             +

Would an atom have a
nucleus if the strong
force did not exist?
Weak Force
• This force plays a key         Notice how the original
role in the possible        particle changes to something
change of sub-atomic                     new.
particles.
– For example, a neutron
can change into a                     n
proton(+) and an                     +
electron(-)                           -
• The force responsible
– Radioactive decay 
process in which the
nucleus of a
atom releases nuclear
Isotopes
• Atoms that have the same number of protons,
but have different numbers of neutrons
• Examples      Notice that each of these atoms have one proton;
therefore they are all types of hydrogen. They
just have a different mass number (# of neutrons).

-

-
+                            +                            +

-
Hydrogen (Protium)       Hydrogen (Deuterium)           Hydrogen (Tritium)
Atomic Mass
•    The weighted average of the masses of all the naturally occurring isotopes
of an element
•    The average considers the percent abundance of each isotope in nature
•    Found on the periodic table of elements
•    Example
What would be the atomic mass (≈) of Hydrogen if these three isotopes
were found in the following percentages (99.9, 0.015, 0) respectively?

-

+                              +
+             -

-
Hydrogen (Protium)              Hydrogen (Deuterium)                Hydrogen (Tritium)
Mass # = 1 amu                   Mass # = 2 amu                    Mass # = 3 amu
If you simply average the three, 2 amu (1 amu + 2 amu + 3 amu/3) would be the atomic mass,
but since 99.9% of the Hydrogen is Protium, the atomic mass is around 1 amu (.999 x 1 amu)
Ion
• Charged particle
that typically
results from a loss                             -                  -
or gain of
electrons                             = 8
-
+
• Two types:                            = 8             ++ +
– Anion = negatively                      -        + + +             -
charged particle              -    8
=9
6
– Cation = positively
+  +
charged particle                       -           -
Now that this electrons were just
Currently, this atom oxygen lost,
Now that threeatom ofof oxygen is                              -
gained an because it it is no longer
the number of electronsan equal
-
neutral electron, has (6) and
protons (8) is still (8) and now
neutral electrons unbalanced;
number of or an atom. It is protons
therefore, it ion (anion). This now it
considered an is still an ion, but ion has
(8).
more electrons (9) than as a cation.
is specifically referred toprotons (8).              Symbol = O
Symbol = O2+
1-
Building Ions
Using the expo marker and your desk, draw
the following ions, and determine their atomic
numbers and their atomic mass numbers.
Ions             Protons         Neutrons         Electrons
Carbon (C³¯)               6                 6               9
Hydrogen (H¹+)             1                 0               0
Oxygen (O²¯)               8                 8               10
Lithium (Li³+)             3                 4               0
Sodium (Na¹¯)              11               12               12
Be aware that the atomic and mass numbers are not
impacted by the loss or gain of electrons.
And that’s….

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 views: 72 posted: 7/18/2010 language: English pages: 32