# 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       __________
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 _
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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