General orrganic and biological chemistry structures off liffe 5th CH5 natural radioactivity GOB structures 5th ed

Lecture Presentation

Chapter 5
Nuclear
Chemistry

Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 5 Nuclear Chemistry
A nuclear medicine
technologist works in a
hospital where nuclear
medicine is used to diagnose
and treat a variety of medical
conditions. The technologist
prepares the radioisotopes
given to patients and uses a
scanner that converts the
radiation from various parts
of the body into images.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

Chapter 5 Readiness
Key Math Skills
• Using Positive and Negative Numbers in Calculations
(1.4B)
• Solving Equations (1.4D)
• Interpreting a Graph (1.4E)
Core Chemistry Skills
• Using Conversion Factors (2.6)
• Counting Protons and Neutrons (4.4)
• Writing Atomic Symbols for Isotopes (4.5)
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


5.1 Natural Radioactivity
In a nuclear pharmacy, a
person working with
radioisotopes wears
protective clothing and
gloves and uses a lead
glass shield on a syringe.
Learning Goal Describe
alpha, beta, positron, and
gamma radiation.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Natural Radioactivity
Radioactivity comes from unstable nuclei, which are
• found in elements with atomic numbers 20 and higher.
• defined as nuclei in which the nuclear forces cannot offset
the repulsions between the protons.
• radioactive, emitting small particles of energy called
radiation to become more stable.
Radiation may take the form of alpha (α) and beta (β) particles,
positrons (β+), or pure energy such as gamma (γ) rays.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Radioisotope
A radioisotope
• is an isotope of an element that emits radiation.
• can be one or more isotopes of an element.
• includes the mass number in its name.
The atomic symbol for iodine-131, a radioisotope used in the
diagnosis and treatment of thyroid disorders, has a mass
number of 131 and an atomic number of 53.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake

© 2016 Pearson Education, Inc.


Stable and Radioactive Isotopes

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Types of Radiation
Radioisotopes emit
radiation such as
• alpha (α) particles,
identical to a helium
nucleus,
.
• beta (β) particles, high
energy electrons, .
• positrons (β+),

.

• pure energy called
gamma (γ) rays, .
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Some Forms of Radiation

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check
Identify and write the symbol for each of the
following types of radiation.
A. alpha particle
B. positron
C. beta particle

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
Identify and write the symbol for each of the
following types of radiation.
A. alpha particle
B. positron

C. beta particle

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Biological Effects of Radiation
Ionizing radiation strikes
molecules in its path and
• knocks away the electrons in
molecules, forming unstable
ions such as H2O+.
• causes undesirable chemical
reactions.
• damages the cells most
sensitive to radiation, rapidly
dividing cells in bone marrow,
skin, and reproductive organs,
thus causing cancer.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

Different types of radiation
penetrate the body to
different depths.
© 2016 Pearson Education, Inc.

Radiation Protection
Radiation protection requires
• paper and clothing for blocking alpha particles.
• a lab coat or gloves for blocking beta particles.
• dense shielding such as lead or concrete to block
gamma rays.
For those working in an environment where radioactive
materials are present, limit your exposure by
• minimizing the amount of time spent near a radioactive
source.
• increasing the distance from the source.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Properties of Radiation

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check
Indicate the type of radiation (alpha, beta, and/or
gamma) protection for each type of shielding.
A. heavy clothing
B. paper

C. lead
D. thick concrete

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
Indicate the type of radiation (alpha, beta, and/or
gamma) protection for each type of shielding.
A. heavy clothing alpha, beta
B. paper
alpha
C. lead
alpha, beta, gamma
D. thick concrete
alpha, beta, gamma

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

5.2 Nuclear Reactions
In the nuclear equation
for alpha decay, the
mass number of the
new nucleus decreases
by 4 and its atomic
number decreases by 2.
Learning Goal Write a
balanced nuclear equation
showing mass numbers
and atomic numbers for
radioactive decay.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Balancing Nuclear Equations
In a process called radioactive decay, the nucleus breaks
down by emitting radiation. The process is represented by a
nuclear in which
• the mass number and atomic number may change.
• the sum of the mass numbers and the sum of the atomic
numbers are equal for the reactants and the products:
Mass number sum:
251
=

251
251
247
Cf 98
Cm96 + 4He 2
Atomic number sum:

98

=

98

Core Chemistry Skill Writing Nuclear Equations
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Alpha Decay
Alpha decay occurs when
a radioactive nucleus
emits an alpha particle,
forming a new nucleus
with a mass number that
is decreased by 4 and an
atomic number that is
decreased by 2.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Guide to Completing Nuclear Equations

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Equation for Alpha Emission

4
He
2

Complete the following nuclear equation for the decay of
americium-241:

ANALYZE         Given            Need
THE PROBLEM       Am­241,                  balanced nuclear equation
        alpha decay

STEP 1 Write the incomplete nuclear equation.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake

© 2016 Pearson Education, Inc.


Equation for Alpha Emission 42 He
Complete the following nuclear equation for the decay of
americium-241:

STEP 2 Determine the missing mass number.
241
=? + 4
241 − 4 = ?
241 – 4 = 237 (mass number of new nucleus)
STEP 3 Determine the missing atomic number.
95
=? + 2
95 – 2
=?
95 − 2 = 93 (atomic number of new nucleus)
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Equation for Alpha Emission 42 He
Complete the following nuclear equation for the decay of
americium-241:

STEP 4 Determine the symbol of the new nucleus.
The element that has atomic number 93 is neptunium,
Np.
STEP 5 Complete the nuclear equation.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Beta Decay –10e
In the nuclear equation
for beta decay, a beta
particle, an electron, is
emitted from the nucleus
when a neutron in the
nucleus breaks down,
forming a proton and a
beta particle and
increasing the atomic
number by 1.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.