Symbols of Elements by JLHXlGjv

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									       The Atom,
Atomic Number and Mass
      Number, and
        Isotopes

                         1
            Atomic Theory



 Atoms are building blocks of elements
 Atoms are similar for each element
 Two or more different atoms bond in simple
 ratios to form compounds


                                          2
         Subatomic Particles

Particle   Symbol   Charge   Relative
                             Mass

Electron   e-       1-        0

Proton     p+       +         1

Neutron    n        0         1

                                        3
Location of Subatomic Particles

              10-13 cm
 electrons


                         protons
               nucleus   neutrons




   10-8 cm                          4
Atomic Number

Counts the number
        of
     protons
   in an atom


                    5
           Periodic Table

 Represents physical and chemical
  behavior of elements
 Arranges elements by increasing atomic
  number
 Repeats similar properties in columns
  known as chemical families or groups


                                           6
         Periodic Table
1    2          3   4   5   6   7   8


11
Na




                                    7
      Atomic Number on the
         Periodic Table


Atomic Number
                11
Symbol
                Na
                             8
  All atoms of an element have
  the same number of protons

11 protons
                11
Sodium
               Na
                                 9
       Learning Check AT 1
State the number of protons for atoms of
each of the following:
A. Nitrogen
1) 5 protons     2) 7 protons 3) 14 protons
B. Sulfur
1) 32 protons   2) 16 protons   3) 6 protons
C. Barium
1) 137 protons 2) 81 protons    3) 56 protons
                                          10
            Solution AT 1
State the number of protons for atoms of each
of the following:
A. Nitrogen
    2) 7 protons
B. Sulfur
    2) 16 protons
C. Barium
   3) 56 protons
                                          11
         Number of Electrons



 An atom is neutral
 The net charge is zero
 Number of protons = Number of electrons
 Atomic number = Number of electrons


                                        12
  Mass Number


 Counts the number
          of
protons and neutrons
     in an atom


                       13
           Atomic Symbols

 Show the mass number and atomic number
 Give the symbol of the element


 mass number
                    23 Na          sodium-23
 atomic number      11


                                           14
       More Atomic Symbols


16          31        65
  O          P             Zn
 8          15        30
8 p+        15 p+     30 p+
8n          16 n      35 n
8 e-        15 e-     30 e-     15
                Isotopes

 Atoms with the same number of protons,
 but different numbers of neutrons.
 These atoms have the same atomic number
 but have different atomic mass numbers.
        Isotopes of chlorine
         35Cl           37Cl
         17             17

   chlorine - 35    chlorine - 37      16
             Learning Check
 Naturally occurring carbon consists of three
 isotopes, 12C, 13C, and 14C. State the number of
 protons, neutrons, and electrons in each of
 these carbon atoms.
    12C              13C             14C
     6                6               6

#P _______        _______          _______
#N _______        _______           _______
#E _______        _______          _______    17
            Solution


    12C       13C       14C
    6          6         6

#P __6___   _ 6___     ___6___

#N __6___   _ _7___    ___8___

#E __6___   _ 6___     ___6___


                                 18
         Learning Check AT 3
An atom of zinc has a mass number of 65.
  A. Number of protons in the zinc atom
    1) 30           2) 35           3) 65

  B. Number of neutrons in the zinc atom
    1) 30           2) 35           3) 65

 C. What is the mass number of a zinc isotope
     with 37 neutrons?
     1) 37           2) 65          3) 67
                                            19
              Solution AT 3
An atom of zinc has a mass number of 65.
  A. Number of protons in the zinc atom
    1) 30
  B. Number of neutrons in the zinc atom
     2) 35

 C. What is the mass number of a zinc isotope
     with 37 neutrons?
     3) 67
                                           20
        Learning Check AT 4

Write the atomic symbols for atoms with
the following:

A. 8 p+, 8 n, 8 e-     ___________

B. 17p+, 20n, 17e-     ___________

C. 47p+, 60 n, 47 e-   ___________
                                          21
             Solution AT 4

                       16O

A. 8 p+, 8 n, 8 e-     8


B. 17p+, 20n, 17e-     37Cl
                       17

C. 47p+, 60 n, 47 e-   107Ag
                       47
                               22
           Learning Check AT 5
An atom has 14 protons and 20 neutrons.
 A. Its atomic number is
     1) 14          2) 16           3) 34
 B. Its mass number is
    1) 14          2) 16            3) 34
 C. The element is
    1) Si          2) Ca            3) Se

 D. Another isotope of this element is
     1)   34X       2)   34X        3)   36X
          16             14              14
                                               23
              Solution AT 5
An atom has 14 protons and 20 neutrons.
 A. It has atomic number
     1) 14

 B. It has a mass number of
    3) 34

 C. The element is
    1) Si
 D. Another isotope of this element would be
     3) 36X
                                          24
       14
           Masses of Atoms
 A scale designed for atoms gives their small
  atomic masses in atomic mass units (amu)
 An atom of 12C was assigned an exact mass of
  12.00 amu
 Relative masses of all other atoms was
  determined by comparing each to the mass of
  12C

 An atom twice as heavy has a mass of 24.00
  amu. An atom half as heavy is 6.00 amu. 25
               Atomic Mass
                                        Na
                                       22.99
 Listed on the periodic table
 Gives the mass of “average” atom of each
  element compared to 12C
 Average atom based on all the isotopes and their
  abundance %
 Atomic mass is not a whole number
                                             26
     Learning Check AT6
Using the periodic table, specify the
atomic mass of each element (round to the
tenths place):
A. calcium        __________
B. aluminum       __________
C. lead           __________
D. barium         __________
E. iron           __________
                                       27
            Solution AT6
Using the periodic table, specify the
atomic mass of each element (round to the
tenths place):
A. calcium        _40.1 amu _
B. aluminum       _27.0 amu _
C. lead           _207.2 amu_
D. barium         _137.3 amu_
E. iron           _55.8 amu__
                                       28
     Calculating Atomic Mass

 You need the % abundance and mass of
 each isotope
 Weighted average =
  mass isotope1(%) + mass isotope2(%) + …
      100                100



                                         29
    Atomic Mass of Magnesium
 Isotopes    Mass of Isotope   Abundance
 24Mg    =   24.0 amu           78.70%
 25Mg    =   25.0 amu           10.13%
 26Mg    =   26.0 amu           11.17%
Atomic mass (average mass) Mg = 24.3 amu

     Mg
     24.3                                30
          Learning Check


Gallium is a metallic element found in
small lasers used in compact disc players.
In a sample of gallium, there is 60.2% of
gallium-69 (68.9 amu) atoms and 39.8% of
gallium-71 (70.9 amu) atoms. What is the
atomic mass of gallium?

                                        31
                 Solution AT7
Ga-69
68.9 amu x      60.2   =   41.5 amu for   69Ga

                100
Ga-71 (%/100)
70.9 amu x 39.8        =   28.2 amu for   71Ga

                100

Atomic mass Ga =           69.7 amu
                                             32
   Finding the % Abundance
A sample of boron consists of 10B (mass
10.0 amu) and 11B (mass 11.0 amu). If
the average atomic mass of B is 10.8
amu, what is the % abundance of each
boron isotope?




                                    33
Assign X and Y values:
 X = % 10B       Y = % 11B
Determine Y in terms of X
 X     +    Y       = 100
 Y = 100 - X

Solve for X:
 X (10.0) + (100 - X )(11.0)   = 10.8
    100           100
Multiply through by 100
 10.0 X + 1100 - 11.0X = 1080
                                        34
Collect X terms
10.0 X - 11.0 X       =   1080 - 1100

    - 1.0 X = -20

     X    =     -20       =   20 %   10B

              - 1.0
Y = 100 - X
  % 11B = 100 - 20% =          80% 11B

                                           35
     Learning Check AT8

Copper has two isotopes 63Cu (62.9
amu) and 65Cu (64.9 amu). What is the
% abundance of each isotope? (Hint:
Check periodic table for atomic mass)

1) 30%      2) 70%         3) 100%



                                        36
              Solution AT8
     2) 70%

Solution

 62.9X + 6490 = 64.9X = 6350
    -2.0 X = -140
         X = 70%

                               37

								
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