Transcript The Nucleus - Madison Public Schools

The Nucleus
Objectives:
1. Relate nuclear stability to the ratio
of neutrons to protons
2. Describe the forms of radioactive
decay
3. Balance decay equations
The Nucleus
Definitions:
nucleons-protons and neutrons collectively
nuclide- a specific atom (in nuclear chemistry)
mass defect – difference between the actual mass
of an atom and the sum of the masses of all of
an atom’s protons, neutrons, and electrons
Nuclear binding energy – energy released when a
nucleus is formed from nucleons (E = mc2)
Binding Energy per Nucleon
•Higher binding energy/nucleon
 higher nuclear stability
Band of Stability
•Small atoms tend to
have neutron-proton
ratios ~ 1:1
•The ratio approaches
1.5:1 as the atomic
number increases
•Explained by the
relationship between
strong nuclear forces
and electrostatic
repulsion
Nucleons and nuclear stability
• Strong nuclear forces act
over very short distances
• As the # of protons
increases, the
electrostatic force
between protons
increases
• More neutrons are
needed to stabilize the
nucleus
Nuclear Reactions
Transmutation –
transformation of one
element into another
• Nuclear reactions occur
when unstable nuclei
undergo changes in the #
of protons and neutrons
in order to increase
stability
• Large amounts of energy
are given off
Nuclear Reactions
9
4
Be  He  C  n
4
2
12
6
1
0
•In nuclear equations, the sum of atomic #’s
and mass #’s must be equal on both sides of
the equation.
Complete the following nuclear reactions:
218
84
253
99
Es
142
61
Po 

He  ???
4
2
He 
4
2
Pm  ??? 
n  ???
1
0
142
60
Nd