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|  DOE-HDBK-1130-98
II.
MODULE OUTLINE
A. Atomic Structure
1.
The basic unit of matter is the atom. The three basic particles of the atom are protons,
neutrons, and electrons. The central portion of the atom is the nucleus. The nucleus
consists of protons and neutrons. Electrons orbit the nucleus.
a.
Protons
1)
Protons are located in the nucleus of the atom.
2)
Protons have a positive electrical charge.
3)
The number of protons in the nucleus determines the element.
b.
Neutrons
1)
Neutrons are located in the nucleus of the atom.
2)
Neutrons have no electrical charge.
3)
Atoms of the same element have the same number of protons, but can have a
different number of neutrons.
4)
Atoms which have the same number of protons but different numbers of neutrons
are called isotopes.
NOTE: Common notation for describing isotopes is to list the atomic symbol for an
element followed by its mass number . The mass number is the sum of protons and
neutrons. For example, tritium has 1 proton and 2 neutrons, and is denoted as H-3.
5)
Isotopes have the same chemical properties; however, the nuclear properties can be
quite different.
c.
Electrons
1)
Electrons are in orbit around the nucleus of an atom.
2)
Electrons have a negative electrical charge.
3) This negative charge is equal in magnitude to the proton's positive charge.
3
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