Transcript 25.1 Notes - Trimble County Schools

Chapter 25 – Nuclear Changes
25.1 - Radioactivity
Objectives
• Describe the structure of an atom
and its nucleus.
• Explain what radioactivity is.
• Compare and contrast properties of
radioactive and stable nuclei.
• Discuss the discovery of
radioactivity.
Nucleus
•Composed of protons and neutrons
which account for most of the atom’s
mass
Strong force
•Causes protons and neutrons to be
attracted to each other in the nucleus
Video clip
• The strong force is powerful
only when neutrons and
protons are close to each
other
• The protons and neutrons in
a large nucleus are held less
tightly by the strong force
than those in a small nucleus
Radioactivity
•The nuclear decay that occurs when
the strong force is not large enough
to hold the nucleus together and the
nucleus gives off matter and energy
Isotopes
•Atoms of the same element with
varying number of neutrons
•A nucleus with too many or too
few neutrons compared to
protons is radioactive
–Atomic number = number of
protons in an atom
–Mass number = number of protons
and neutrons in a nucleus
Symbol
1
1
H
235
92
U
Atomic
Number
Number
of
protons
Mass
Number
Number
of
Neutrons
1
1
1
0
92
92
235
235-92 =
143
Element Radioactivity
•Uranium was discovered in 1896 by
Henri Becquerel as a radioactive
element
•Polonium and Radium were
discovered as radioactivity by Marie
and Pierre Curie in 1898
Video Clip
Thinking Stem Log
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I was successful in…
I get stuck…
I figured out…
I get confused when… so I…
I didn’t expect…
I think I need to redo…
I need to rethink...
I’m not sure…
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What puzzles me the most is…
I was really surprised when…
I will understand this better if I…
I stopped …because…
The hardest part of this is…
I figured it out because…
I really feel good about the
way…
In-Class Assignment/Homework
• 25.1 Reinforcement WKT
– 25.1 Enrichment WKT
– 25.1 & 25.2 Directed Reading WKT