The Building Blocks of Matter Atoms

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					The Building Blocks of Matter:
            Atoms


        -            -

              -

             ++ +
    -       + + +        -
             +  +
              -

        -            -
  Note-Taking Instructions
• As 8th graders, you will be responsible for
  organizing your own notes this year. No
  more “cookie-cutter” notes.
• 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
  for radioactive decay.
   – Radioactive decay 
     process in which the
     nucleus of a
     radioactive (unstable)
     atom releases nuclear
     radiation.
                          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….