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					    Atoms


T. M. Yeung 2000
   What is the particle that made up an
    element?
Atoms
 All elements are made
  up of small particles
  called atoms.
 Different elements
  have their unique kind
  of atoms.
 The atoms of iron are
  different from that of
  carbon.
Gold and its Atoms
Different Elements are made up
of different atoms
       a silver          a copper
       wire              wire



       silver atoms     copper atoms
       enlarged many,   enlarged many,
       many times       many times
Basic Structure of Atom

       electron




                  neutron




                    proton
Solar System
Basic Structure of Atom
Particle   Symbol   Relative   Relative
                     Mass      Charge
 Proton      p         1         +1
 (質子)
Electron     e-     1/18400      -1
 (電子)
Neutron      n         1          0
 (中子)
Atomic Number & Mass Number
   An Atom is electrically neutral, that means
   No. of proton(s) in an atom
    = No. of electron(s) in the same atom
   Atomic Number (Z) of an atom
    = No. of proton(s) of the atom
   Mass Number (A) of an atom
    = No. of proton(s) + No. of neutron(s)
Example
   What is the atomic number and the mass number
    of the atom shown below? Atomic number is 2
                              and mass number is 4
                                neutron


                                electron



                                proton


                                 nucleus
Class-work
Atom Symbol Atomic Mass No. of No. of No. of
            no. (Z) no. (A) proton neutron electron

Hydro H       1      1       1      0       1
gen
Beryll Be     4      9       4      5       4
ium
Sodiu Na      11     23      11     12      11
m
Notation of Atom
 X = symbol of element
 Z = atomic number
 A = mass number
                          A
                          Z   X
Notation of Atom
   Atomic no. =?
   92
   Mass no. =?
                            235



    235
    No. of the neutron =?
    143                      92   U
   Name =?
   Uranium
Atomic Bombing at Nagasaki
Class-work

 Atom    No. of No. of No. of
         proton neutron electron
 35
 17 Cl     17     18       17
 27
 13 Al     13     14       13
 40
 20 Ca     20     20       20
  31
  15 P     15     16       15
Isotopes of Hydrogen
Isotopes of Hydrogen
  Name       Symbol   Atomic   Mass no.
                        no.
Hydrogen-1    1          1        1
              1   H
Hydrogen-2    2         1         2
              1   H
Hydrogen-3    3         1         3
              1   H
Chemistry Dictation
   First 20 elements
   10 minutes:
Relative Atomic Mass
   The mass of a hydrogen atom is only
    1.66 x 10-24g!
   The mass of a carbon atom is only
    2 x 10-23g!
    (0.00 000 000 000 000 000 000 002g!)
   Carbon-12 atom is being taken as the
    reference standard.
   The relative atomic mass of carbon-12
    atom is defined as 12 units.
Relative Atomic Mass
   Most elements have more than one isotope,
    and different isotopes have different masses.
   The relative atomic mass of an element is
    the average mass of its isotopes compare
    with an atom carbon-12.
   Isotope        Percentage abundance
    35Cl                75%
    37Cl                25%
   Relative atomic mass of chlorine, Cl:
    75/100 x 35 + 25/100 x 37
    = 35.5 (a.m.u.) #
   Relative atomic mass of lead, Pb:
    2/100 x 204 + 24/100 x 206 + 22/100 x 207
    + 52/100 x 208
    = 207.2 (a.m.u.) #
Electron Arrangement of Atoms
                                  Maximum
                                   Number
                Shell                 of
              Number (n)        Electrons (2n2)
                 1                     2
                  2                   8
                  3                   18




                      nucleus
Electron Arrangement of Atoms
 Oxygen atom
 Atomic no. = 8
 No. of protons
  = No. of electrons
                         O
  =8
 Electron arrangement
  = 2, 6

                             Electron
Electron Arrangement of Atoms
 Oxygen atom
 Atomic no. = 8
 No. of protons
  = No. of electrons
                         O
  =8
 Electron arrangement
  = 2, 6

                             Electron
Electron Arrangement of Atoms
 Oxygen atom
 Atomic no. = 8
 No. of protons
  = No. of electrons
                         O
  =8
 Electron arrangement
  = 2, 6

                             Electron
Electron Arrangement of Atoms
 Oxygen atom
 Atomic no. = 8
 No. of protons
  = No. of electrons
                         O
  =8
 Electron arrangement
  = 2, 6

                             Electron
Electron Diagram of Oxygen
Atom
                  Two electrons in the
                   first shell.
                  Six electrons in the
                   second shell.
       O
                  Electron arrangement
                   = 2, 6


      electron
Electron Diagram of Aluminium
Atom
                  Atomic no. = 13
                  Electron arrangement
                   =2, 8, 3
                  Two electrons in the
      Al
                   first shell.
                  Eight electrons in the
                   second shell.
                  Three electrons in the
                   third shell
Electron Diagram of Magnesium
Atom
               Atomic no. = 12
               Electron arrangement
                = 2, 8, 2
      Mg
Electron Diagram of Fluorine
Atom
                Atomic no. = 9
                Electron arrangement
                 = 2, 7
       F
Electron Diagram of Boron Atom
                Atomic no. = 5
                Electron arrangement
                 = 2, 3
       B
Simple Ions
 A simple ion is formed
  when an atom either
  loses or gains one or
  more electrons.
 It is either positively
  or negatively charged.
 Positive ions are called
  cations.
Simple Ion
Simple Ion: Cation
                Lithium atom, Li:
                Atomic no. = 3
                Electron arrangement
                 = 2, 1
       Li
                Remove one electron
                 from the outermost
                 shell of lithium atom...
Simple Ion: Cation
                  Lithium ion, Li+:
           +      Atomic no. = 3
                  Electron arrangement
                   =2
     Li
                  Three protons
                  Two electrons
                  Positively charged
                   particle!
Simple Ion: Anion
                Fluorine atom, F:
                Atomic no. = 9
                Electron arrangement
                 = 2, 7
       F
                Add one electron to
                 the outermost shell of
                 fluorine atom...
Simple Ion: Anion
                                 -
              -  Fluoride ion, F :
                   Atomic no. = 9
                   Electron arrangement
      F             = 2, 8
                   Nine protons
                   Ten electrons
                   Negatively charged
                    particle
    References
   Atomic Bomb
    • http://www.geocities.com/Athens/Agora/4526/i
      ndex1.html
   Encarta 98
   General Chemistry
    • http://www-
      wilson.ucsd.edu/education/gchem/index.html
   General Chemistry I -- A Virtual Textbook
    • http://wine1.sb.fsu.edu/chm1045/chm1045.htm

				
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