Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 107

Fundamentals of Chemistry

Fall 2009

Lecture Notes: 8 September

© R. Paselk 2009



Isotopes are forms of elements which differ only in the number of neutrons. This means different isotopes of the same element have essentially the same chemical properties but slightly different physical properties. They can also different substantially in terms of their nuclear stability. Let's finish our table of examples of isotopes:







14 6 14 6 8 6
238U6+ ? ? ? ? ?
35Cl- ? ? ? ? ?
?O? ? 18 ? ? 10 

You should be able to fill in the blanks in a table like this with, the aid of a periodic table, on a quiz.

Determination of Atomic Mass:

We want to be able to figure out the atomic mass of a sample with a particular isotopic composition.

Example: Cu occurs as an isotopic mixture of 69.09% 63Cu (mass = 62.93 amu) and 30.91% 65Cu (64.93 amu). What is the atomic mass of copper in this sample.

Chemical Periodicity

Look at the Periodic Chart on the wall.

You should know the terminology above and memorize the names and symbols for the elements shown in the table below.

Periodic Table of the Elements
1 2 13 14 15 16 17 18
   H  He
Li Be    B C N O F Ne
Na Mg 3 4 5 6 7 8 9 10 11 12  Al Si P S Cl Ar
K Ca   Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb Sr                  Ag  Cd   Sn     I  Xe
 Cs  Ba        W        Pt Au  Hg    Pb        

Let's look at some of the elements and see what their properties are like:

2 Na + 2 H2O right arrow 2 Na+ + 2 OH- + H2

2 Na + Cl2 right arrow 2 NaCl

Predicting the charges of elemental ions.

Transition metal ions

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© R A Paselk

Last modified 8 September 2009