Stability Graph
Chlorine atoms have 17 electrons. This is the same as the atomic number of
Chlorine. Chlorine atoms can have different numbers of neutrons. Chlorine 35
(atomic mass) has 18 neutrons. Chlorine 37 has 20 neutrons. Cl 35 and Cl 37 are
called isotopes of Chlorine. If the n/p (neutron/proton) ratio is far from one, the
atom will be radioactive and decompose.
Procedure:
1. Complete the data table.
2. Graph the elements, X-axis protons, Y-axis neutrons. Create a scale that uses
the whole graph paper. Connect the points in a smooth curve.
Data:
Element
Symbol
Boron 11
Oxygen 16
Magnesium
24
Silicon 28
Chlorine 35
Calcium 40
Chromium
52
Cobalt 59
Zinc 65
Bromine 80
Strontium
87
Molybdenum
96
Silver 108
Tin 119
Iodine 127
Barium 137
Tungsten
184
Iridium 190
Gold 197
Argon 40
Neutrons
Protons
Ratio n/p
Stability Graph Part II
1. Graph the following isotopes in a different color on the same graph from part
I. Use your graph to decide which of the following elements will be radioactive. If
they are, determine which particle it will emit and write the nuclear equation for
the decay in the following data table.
Nuclei of elements that lie to the left of the band of stability & have
a ratio  1 or (1.5 if atomic number greater than 20) have too many
neutrons and will usually decay by emitting Beta particles. Nuclei of
elements that lie to the right of the band of stability & have a ratio 1 or
(1.5 if atomic number greater than 20) have too many protons and will
decay by electron capture or positron emission. Nuclei of elements that
are above the band of stability or have an atomic number greater than 83
have too many protons and neutrons and will decay by emitting alpha
particles.
Isotope
Symbol
Neutrons
Protons
Ratio
n/p
Is it
Radioactive
Type of
Emission
Nuclear Equation
Carbon 14
Polonium 210
Nitrogen 14
Magnesium 20
Neon 20
Sulfur 35
Curium 248
Strontium 90
Carbon 12
Nickel 59
Questions:
1. If a nucleus has too many protons, explain what type of emission will solve
the problem and why?
2. If a nucleus has too many neutrons, explain what type of emission will
solve the problem and why?