Determining the number of atomic particles in an element by pptfiles

VIEWS: 0 PAGES: 32

									Determining the number
of atomic particles in an
element
Step one


    Find the element on
    the periodic table.
     Find oxygen.
On your paper WRITE



     1. Find the
     element on the
     periodic table.
Step Two


 •Find the number
  of protons (+).
           8
                O
                oxygen
               15.99
     On your paper WRITE


2.Find the number of
 protons (+).
 A. Atomic # = number of
  protons
Hint: Find the atomic
number.
 • The atomic number is
   equal to the number
   of protons (+)
       8
            O
            oxygen
           15.99
Eight is the atomic
number.

•This means oxygen
 has 8 protons (+).
        8
             O
             oxygen
            15.99
Check for Understanding

  • How many protons (+)
    does copper have?

         29            29
              Cu
              Copper   protons
          63.55
Check for Understanding

  • How many protons (+)
    does lead have?

         82          82
              Pb
              Lead   protons
          207.20
Step Three


 •Find the number
  of electrons (-).
        8
             O
             oxygen
            15.99
Hint: Find the atomic
number.
• The atomic number is
  equal to the number of
  electrons (-) in a neutral
  atom.
         8
              O
              oxygen
             15.99
Whoa! What is a neutral
atom?

 • Neutral means not positive
   and not negative. So the
   number of protons (+) have
   to equal the number of
   electrons (-) to cancel each
   other out.
So if eight is the atomic
number of oxygen.

 • Then oxygen has 8 protons
   (+).
 • Which means oxygen has 8
   electrons (-).
                  8
                     O
                    oxygen
                   15.99
Check for Understanding

  • The number of + will
    always EQUAL the
    number of - in a neutral
    atom.
  • # of protons = # of electrons
Check for Understanding

  • How many electrons (-)
    does copper have?

         29            29
              Cu
              Copper   electrons
           63.55
Check for Understanding

  • How many electrons (-)
    does lead have?

         82          82
              Pb
              Lead   electrons
           207.20
     On your paper WRITE


3.Find the number of
 electrons (-).
 A. # of protons = # of
  electrons
Now What!?!


  • The atomic number gives
    us the number of protons
    (+) and the number of
    electrons (-).
  • A.P.E.
  • Atomic # = Proton # = Electron #
Now What!?!


  • But how do we get the
    number of neutrons (no
    charge)?
Step four--number of neutrons


   • To get the the number of
     neutrons, we have to do
     TWO things
   • Round the atomic mass.
   • Subtract the atomic
     number from the rounded
     atomic mass.
Where is the atomic
mass?

•The bottom number
 is the atomic mass.
      8
           O
           oxygen
          15.99
What is the atomic
mass?
• The atomic mass is the average
  mass of one atom of that
  element.
• One atom of Oxygen has a
  mass of 15.99 amu. 8
                          O
                         oxygen

                        15.99
     Round the atomic mass.

    • To round to the nearest
      WHOLE NUMBER, you look
      at the tenths column..
                       8
For oxygen, the             O
                            oxygen
number in the tenths
column is 9                15.99
     Round the atomic mass.

    • If the number in the tenths
      column is 5, 6, 7 , 8 or
      9…you add one to the ones
      column.
                            8
For oxygen, the                 O
                               oxygen
rounded amount is
16.
                              15.99
   Round the atomic mass.

   • If the number in the tenths
     column is 4, 3, 2, 1 or 0, you
     simply drop the decimals.
For magnesium,           12
the rounded                   Mg
                              magnesium
amount is 24.              24.30
Okay, so we have rounded
the atomic mass..NEXT?
 • To get the the number of
   neutrons, we have to do
   TWO things
 • Round the atomic mass.
 • Subtract the atomic
   number from the rounded
   atomic mass.
Subtract the atomic number
from the rounded atomic mass.
   • The rounded atomic mass
     for oxygen is 16.
   •The atomic number is 8.
      16              8
     - 8
    _________
                           O
        8                  oxygen

                          15.99
So the number of neutrons
is … 8.
 • The rounded atomic mass
   for oxygen is 16.
 •The atomic number is 8.
    16              8
  - 8
  _________
                         O
      8 neutrons         oxygen

                        15.99
  On your paper WRITE


4. To find the number of
 neutrons
 A. Round the atomic mass.
 B. Subtract the atomic
  number from the rounded
  atomic mass.
 Check for Understanding

      • How many neutrons (o)
        does copper have?
 64
- 29
_______
             29            35
  35              Cu
                  Copper   neutrons
              63.55
   Check for understanding

    • Number of protons? 12
    •Number of electrons?    12
•Number of neutrons?
                        12
    24
-_________
    12                       Mg
                             magnesium
     12 neutrons            24.30
On your paper WRITE


  A.P.E.
  • Atomic # = Proton # = Electron #

  M.A.N.
  • Atomic Mass – Atomic # = Neutron #
   Because…
    Atomic Mass = # of Protons + # of Neutrons

								
To top