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CHE 120/140/170 Handout – The Atom and Subatomic Particles
The Atom and Subatomic Particles
We represent atoms with atomic symbols.
For instance, carbon is represented with C. In this
course, you are expected to know the atomic symbols for elements with the following atomic
numbers: 1-38, 47, 48, 50, 53-56, 74, 78-80, 82, 86, 88, 92 and 94.
All atoms are made up of fundamental subatomic particles.
The fundamental subatomic
particles that we will concern ourselves with are the electrons, protons and neutrons. Sometimes
we want to specify how many of these particles are in a particular atom. This can be done by
writing the complete nuclear symbol: ஺௓ܺ. Here X is the atomic symbol, A is the mass number
and Z is the atomic number. Remember that the atomic number is the same as the number of
protons, and since atoms are neutral, it is also the number of electrons! Now, it is easy to
confuse mass number with the atomic mass. These numbers can be similar, but they are
different! The mass number is simply the sum of the protons and the neutrons in an atom. Thus,
it will always be a whole number. The atomic mass is the weighted average of all the isotopes of
that element, so it does not have to be a whole number.
Complete the following table. Be sure to give what is asked for! The first one is done as an
example.
Name
Symbol
Atomic Mass
carbon
C
12.0107 amu
Number
of Protons
6
Number of
Electrons
6
Number of
Neutrons
6
potassium
Mass
Number
12
Complete
Nuclear Symbol
ଵଶ
଺‫ܥ‬
39
6
8
Ag
107
Ag
109
ଶଶ
ଵ଴ܰ݁
238.029 amu
143
3
3
zinc
34
28
58
32.065 amu
33
copper
36
35
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