STABLE AND UNSTABLE ATOMS
After reading this section you will be able to do the following:
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Define the terms "strong force" and "binding energy."
Explain what is meant by a stable atom and and an unstable atom.
How do atomic particles interact?
There are forces within the atom that account for the behavior of the protons, neutrons,
and electrons. Without these forces, an atom could not stay together. Recall that protons
have a positive charge, electrons a negative charge, and neutrons are neutral. According to
the laws of physics,like charges repel each other and unlike charges attract each other
Draw two like charges and show using arrows how they will behave.
So what makes the protons stay together in an atom?
A force called the strong force opposes and overcomes the force of repulsion between
the protons and holds the nucleus together. The energy associated with the strong force
is called the binding energy. The electrons are kept in orbit around the nucleus because
there is an electromagnetic field of attraction between the positive charge of the protons
and the negative charge of the electrons.
Draw a Bohr Model of a hydrogen atom. Use arrows to indicate the forces acting to
keep the electron in it’s orbit.
Does the nucleus of an atom ever lose particles?
In some atoms, the binding energy is great enough to hold the nucleus together. The
nucleus of this kind of atom is said to be stable. In some atoms the binding energy is not
strong enough to hold the nucleus together, and the nuclei of these atoms are said to
be unstable. Unstable atoms will lose neutrons and protons as they attempt to become
stable.
STABLE AND UNSTABLE ATOMS
1. Isotopes are atoms of the same element that have different numbers of
________________in their nucleus.
Ex: the isotopes of hydrogen are:
2. Use the diagram above to answer the following questions:
a. Name the three isotopes of hydrogen. _____________, ____________, and
__________
b. Which isotope of hydrogen has the lowest mass? ______________________ What is
its mass? _______ amu
c. Which isotope of hydrogen has the greatest mass? ______________________ What is
its mass? _______ amu
d. Assuming these atoms are neutral, how many electrons does each of them have?
_______
e. What do the little dots around the protons and neutrons in these pictures
represent?_____________________________
Quiz :
1. ______________________ cause like charges to repel each other and unlike
charges to attract each other.
2. The protons stay together in the nucleus because the ____________ opposes and
overcomes the forces of repulsion from the electromagnetic field.
3. _____________ is the energy that is associated with the strong force, and this
energy holds the nucleus together.
4. A ___________ is an atom that has enough binding energy to hold the nucleus
together permanently.
5. An ____________ does not have enough binding energy to hold the nucleus
together permanently and is called a ____________________
STABLE AND UNSTABLE ATOMS
Quiz (Key):
1. Electromagnetic fields cause like charges to repel each other and unlike charges to
attract each other.
2. The protons stay together in the nucleus because the strong force opposes and
overcomes the forces of repulsion from the electromagnetic field.
3. Binding energy is the energy that is associated with the strong force, and this
energy holds the nucleus together.
4. A stable atom is an atom that has enough binding energy to hold the nucleus
together permanently.
5. An unstable atom does not have enough binding energy to hold the nucleus together
permanently and is called a radioactive atom