NUCLEAR CHEMISTRY
Introduction to Nuclear Chemistry

Nuclear chemistry is the study of the structure of
atomic nuclei and the changes they undergo.
Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds
are broken
Occur when nuclei
emit particles and/or
rays
Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or
rays
Atoms remain
Atoms often
unchanged, although converted into atoms
they may be
of another element
rearranged
Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or
rays
Atoms remain unchanged, although they
may be rearranged
Atoms often converted into atoms of
another element
Involve only valence May involve protons,
electrons
neutrons, and
electrons
Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or
rays
Atoms remain unchanged, although they
may be rearranged
Atoms often converted into atoms of
another element
Involve only valence electrons
May involve protons, neutrons, and
electrons
Associated with small Associated with
energy changes
large energy
changes
Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or
rays
Atoms remain unchanged, although they
may be rearranged
Atoms often converted into atoms of
another element
Involve only valence electrons
May involve protons, neutrons, and
electrons
Associated with small energy changes
Associated with large energy changes
Reaction rate influenced
by temperature,
particle size,
concentration, etc.
Reaction rate is not
influenced by
temperature, particle
size, concentration, etc.
The Discovery of Radioactivity (1895 –
1898):


Roentgen found that invisible rays were emitted
when electrons bombarded the surface of certain
materials.
Becquerel accidently discovered that
phosphorescent uranium salts produced spontaneous
emissions that darkened photographic plates
The Discovery of Radioactivity (1895 –
1898):

Marie Curie isolated the components (uranium
atoms) emitting the rays
 Identified
2 new elements, polonium and radium, on the
basis of their radioactivity
 These findings contradicted Dalton’s theory of
indivisible atoms.


Radioactivity – process by which particles give off
rays
Radiation – the penetrating rays and particles
emitted by a radioactive source
The Discovery of Radioactivity (1895 –
1898):



Isotopes – atoms of the same element with different
numbers of neutrons
Radioisotopes – isotopes of atoms with
unstable nuclei (too many/few neutrons)
Radioactive decay – when unstable nuclei lose
energy by emitting radiation to attain more stable
atomic configurations (spontaneous process)
Chemical Symbols

A chemical symbol looks like…
14
6

C
To find the number of neutrons, subtract the atomic
# from the mass #.
Alpha radiation







Composition – Alpha particles, same as helium nuclei
4
Symbol – Helium nuclei, 2He, α
Charge – 2+
Mass (amu) – 4
Approximate energy – 5 MeV
Penetrating power – low (0.05 mm body tissue)
Shielding – paper, clothing
Beta - radiation








Composition – Beta particles, same as an electron
Origin – neutron turned to a proton + electron
Symbol – e-, βCharge – 1Mass (amu) – 1/1837 (practically 0)
Approximate energy – 0.05 – 1 MeV
Penetrating power – moderate (4 mm body tissue)
Shielding – metal foil
Beta + radiation








Composition – Beta particles, exact opposite of an
electron, called a positron
Origin – proton turned to a neutron + positron
Symbol – e+, β+
Charge – 1+
Mass (amu) – 1/1837 (practically 0)
Approximate energy – 0.05 – 1 MeV
Penetrating power – moderate (4 mm body tissue)
Shielding – metal foil
Gamma radiation







Composition – High-energy electromagnetic
radiation
Symbol – γ
Charge – 0
Mass (amu) – 0
Approximate energy – 1 MeV
Penetrating power – high (penetrates body easily)
Shielding – lead, concrete
Nuclear Stability




Isotope is completely stable if the nucleus will not
spontaneously decompose.
Elements with atomic #s 1 to 20 are very stable.
1:1 ratio of protons : neutrons (p+: n0)
Example: Carbon – 12 has 6 protons and 6
neutrons
Nuclear Stability



Elements with atomic #s 21 to 82 are marginally
stable.
1:1.5 ratio of protons:neutrons (p+ : n0)
Example: Mercury – 200 has 80 protons and 120
neutrons
Nuclear Stability


Elements with atomic #s >82 are unstable and
radioactive.
Examples: Uranium-235 and plutonium-239
Alpha Decay



Alpha decay – emission of an alpha particle (α),
denoted by the symbol 42
Alpha decay causes the mass # to decrease by 4
and the atomic # to decrease by 2.
Atomic # determines the element. All nuclear
equations are balanced with respect to mass #s
AND atomic #s.
Alpha Decay

Example 1: Write the nuclear equation for the
radioactive decay of polonium – 210 by alpha
emission.
Step 4:
1: Determine
2:
3:
Draw the
Write
the arrow.
element
alpha
the other
particle.
that
product
you are
(ensuring
starting with.
everything is balanced).
Mass #
Atomic #
Alpha Decay

Example 2: Write the nuclear equation for the
radioactive decay of radium – 226 by alpha
emission.
Step 4:
1: Determine
2:
3:
Draw the
Write
the arrow.
element
alpha
the other
particle.
that
product
you are
(ensuring
starting with.
everything is balanced).
Mass #
Atomic #
Beta - decay


Beta decay – emission of a beta particle (β-), a fast
moving electron, denoted by the symbol e- or-10 .
Beta decay causes no change in mass number and
causes the atomic number to increase by 1.
Beta- Decay

Example 1: Write the nuclear equation for the
radioactive decay of carbon – 14 by betaemission.
Step 4:
1: Determine
2:
3:
Draw the
Write
the arrow.
element
beta
the other
particle.
that
product
you are
(ensuring
starting with.
everything is balanced).
Mass #
Atomic #
Beta- Decay

Example 2: Write the nuclear equation for the
radioactive decay of zirconium – 97 by beta decay.
Step 4:
1: Determine
2:
3:
Draw the
Write
the arrow.
element
beta
the other
particle.
that
product
you are
(ensuring
starting with.
everything is balanced).
Mass #
Atomic #
Beta + decay


Beta+ decay – emission of a beta particle (β+), a fast
0
moving positron, denoted by the symbol e+ or+1
.
Beta+ decay causes no change in mass number and
causes the atomic number to decrease by 1.
Beta + Decay

Example 1: Write the nuclear equation for the
radioactive decay of calcium – 37 by positron
emission.
Step 4:
1: Determine
2:
3:
Draw the
Write
the arrow.
element
beta
the other
particle.
that
product
you are
(ensuring
starting with.
everything is balanced).
Mass #
Atomic #
Beta+ Decay

Example 2: Write the nuclear equation for the
radioactive decay of potassium – 37 by beta+
decay.
Step 4:
1: Determine
2:
3:
Draw the
Write
the arrow.
element
beta
the other
particle.
that
product
you are
(ensuring
starting with.
everything is balanced).
Mass #
Atomic #
Gamma decay


Gamma rays – high-energy electromagnetic
radiation, denoted by the symbol γ.
γ has no mass (0) and no charge (0). Gamma rays
almost always accompany alpha and beta
radiation. However, since there is no effect on mass
number or atomic number, they are usually omitted
from nuclear equations.
Transmutation

Transmutation – the conversion of one atom of one
element to an atom of a different element
 Spontaneous
radioactive decay is one way that this
occurs (fission)
 Nuclear fusion in the sun
 Artificial transmutation by people with particle
accelerators to create bigger atoms
 Typically
involve neutrons ( 1 n) as reactants or products
0
Review
Type of
Radioactive
Decay
Alpha
Beta Beta +
Gamma
Particle
Emitted
4
2
He
0
-1 e
0
+1 e
α
ββ+
γ
Change in Change in
Mass #
Atomic #
-4
0
0
0
-2
+1
-1
0