Download Atomic Mass

Atomic Mass
Atomic Number (A)
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Number of protons in the nucleus
Atoms of the same element all have the
same number of protons
In a neutral atom, the total number of
protons is equal to the total number of
electrons
Mass Number (Z)
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Total number of protons and neutrons in
nucleus
Electrons are so small, there mass is
insignificant to the atomic mass
Example
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How many protons, neutrons, and electrons
in
3H
1)
235U
2)
3)
carbon-12
4)
magnessium
41Ca2+
5)
81Br 6)
Isotopes
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Atomic masses can be different for atoms
of the same element if they have different
numbers of neutrons
Atoms with different masses are called
Isotopes or Nuclides