Atomic Symbols and Isotopes
mass #
39
atomic # 19
neutrons +
protons
K
element Symbol
protons
# protons = # of electrons for a NEUTRAL atom
How many neutrons are present? 39 - 19 = 20 n0
How many electrons are present? 19 e-
Complete the Table Below
Name
Protons
Neutrons
Atomic
Number
Mass
Number
6
8
6
14
K
19
22
19
41
Pb
82
124
82
206
Symbol
Carbon-14
14
6
Potassium-41
41
19
Lead-206
206
82
C
Radioactivity
 What is radioactivity?
 Radioactivity occurs when an unstable nucleus
spontaneously emits fragments of the nucleus
and/or energy.
Unstable Nucleus = Radioactive
 Why are only some isotopes radioactive?
 The ratio of protons to neutrons in the nucleus
determines whether or not a nucleus is
radioactive.
Depicting Nuclear Reaction
For nuclear reactions,
 the sum of the mass numbers (top numbers) and
 the sum of the atomic numbers (bottom number)
must be the same on both sides.
Mass Numbers:
9 + 4 = 12 + 1
13 = 13 
Atomic Numbers:
4+2= 6+0
6 = 6 
Finding the Missing Nucleus
Th He  ?
234
90
4
2
Mass Numbers
234 = 4 + ?
? = 230
Atomic Numbers
90 = 2 + ?
? = 88
230
88
Ra
Finding the Missing Nucleus
C  e X
14
6
0
1
A
Z
Mass Numbers
14 = 0 + A
A = 14
Atomic Numbers
6 = -1 + Z
Z = 7
14
7
N
Examples of Transmutation Reactions
C  e N
Th He  Ra
234
90
4
2
14
6
230
88
0
1
14
7
3 H  Be  B He
1
1
9
4
8
5
4
2
These are all transmutation reactions because
the elements on the left side are changed to
produce a different element on the right side.
Emissions from Radioisotopes
Type of
Particle
Emitted
Description
Alpha
A Helium
Nucleus
4
2
Beta
A Fast Moving
Electron
0
1
Gamma
Electromagnetic
Radiation
Symbol
Mass
Charge
Why is it
Emitted?
He or 24
4 amu
+2
Nucleus is
too large.
e or 
1
amu
1840
-1
Too many
neutrons
0 amu
0
Too much
energy
0
1
0
0

A radioisotope is a nucleus that is radioactive or unstable.
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
alpha decay of uranium-238.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
U  He 
238
92
4
2
234
90
Th
Mass Number:
238 = 4 + ?
? = 234
Atomic Number:
92 = 2 + ?
? = 90
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
beta decay of iodine-131.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
I  e
131
53
0
1
131
54
Xe
Mass Number:
131 = 0 + ?
? = 131
Atomic Number:
53 = -1 + ?
? = 54
Writing Nuclear Decay Equations
Write the nuclear decay equation the
emission of a gamma ray from carbon-14.
Start your decay equation by writing the symbol
Write the
for the
typean arrow.
for this nucleus
andsymbol
then follow
it with
of decay.
C   C
14
6
0
0
14
6
Mass Number:
14 = 0 + ?
? = 14
Atomic Number:
6=0+?
?=6
Examples of Transmutation Reactions
C  e N
Th He  Ra
234
90
4
2
14
6
230
88
0
1
14
7
3 H  Be  B He
1
1
9
4
8
5
4
2
These are all transmutation reactions because
the elements on the left side are changed to
produce a different element on the right side.
Decay Series for Uranium-238
This diagram
shows the steps
that an isotope
of uranium takes
to reach a
stable isotope,
lead-206.
A Closer Look at the Decay Series
Write a nuclear decay equation for what we occur to
uranium-234 according to this decay series.
U  Th  He
234
92
230
90
4
2
A Closer Look at the Decay Series
Write a nuclear decay equation for what we occur to
lead-210 according to this decay series.
210
82
Pb 
210
83
Bi  e
0
1
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
alpha decay of uranium-238.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
U  He 
238
92
4
2
234
90
Th
Mass Number:
238 = 4 + ?
? = 234
Atomic Number:
92 = 2 + ?
? = 90
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
beta decay of iodine-131.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
I  e
131
53
0
1
131
54
Xe
Mass Number:
131 = 0 + ?
? = 131
Atomic Number:
53 = -1 + ?
? = 54
Writing Nuclear Decay Equations
Write the nuclear decay equation the
emission of a gamma ray from carbon-14.
Start your decay equation by writing the symbol
Write the
for the
typean arrow.
for this nucleus
andsymbol
then follow
it with
of decay.
C   C
14
6
0
0
14
6
Mass Number:
14 = 0 + ?
? = 14
Atomic Number:
6=0+?
?=6
Protecting Ourselves from
Radioactive Particles
Positive Uses of Nuclear Chemistry
Nuclear Power
Nuclear Medicine
Kills Bacteria on Food