Chemistry for Changing Times 11th Edition Hill and Kolb

1
A material is ___________ if it spontaneously
emits energy to become more stable ________ is
the energy or particles emitted from a nucleus by
a radioactive atom _________ refers to the
particles contained in the nucleus protons and
neutrons. So, the Mass Number is equal to the
nucleon number. A ____________ is the
radioactive atom of an element
Natural Radioactivity
The symbols are still the same
Mass number (protons and neutrons) Element Atomic
number (protons)
I
135 53
2

• Types of Radiation
• Alpha (?) an alpha particle contains 2 protons
  and 2 neutrons
• mass number 4
• atomic number 2
• ? or 2He Alpha particle
• Beta (?) a beta particle is a high-energy
  electron. It has a charge -1. Because the
  mass of an electron compared to a proton is so
  small, ? is given a mass number of 0. It is
  produced by a neutron transforming into a proton
  and a (high energy) electron.
• mass number 0
• atomic number -1
• Beta particle ? or -1e

4
0
Gamma (?) a gamma ray is high-energy radiation.
It is released as an unstable nucleus, which
rearranges to a more stable, lower energy
nucleus. There is no mass or charge or symbol
associated with this type of radiation. Energy
only! ? Gamma Ray
3

• Radiation Protection

______________ is a device used to measure
radiation. It consists of a metal tube filled
with a gas (Ar). In the presence of radiation,
the gas produces an electrical current. This
current is amplified to give a click and hence
a readout on a meter.
4
Nuclear Equations alpha emitters Radioactive
decay is the process of a nucleus spontaneously
breaking down by emitting radiation We can
represent this event with a nuclear
equation Radioactive nucleus ? new nucleus
radiation (?,?,?,?)
5
Nuclear Equations
Guide to completing a nuclear equation.
Turn it into a simple math problem! 1. Account
for all the mass 238 234 4 2. Account
for the atomic number 92 90 2
Example 88Ra ? ? 2He 1. Account for
all the mass 2. Account for the atomic
number Therefore
4
226
6
Sample Problem Complete the following nuclear
equation for the decay of americium-241 95 Am
? ? 2He
4
241
Answer Determine the missing mass
number Determine the missing atomic
number Determine the symbol of the
nucleus Complete the nuclear
equation
7
Nuclear Equations beta emitters Radioactive
nucleus ? new nucleus radiation
(?,?,?,?)
Turn it into a simple math problem! 1. Account
for all the mass 14 14 0 2. Account for
the atomic number 6 7 -1
8
Sample Problem Cobalt-60 decays by emitting a
beta particle. Write the nuclear equation for
its decay.
Answer Write the incomplete nuclear
equation Determine the missing mass
number Determine the missing atomic
number Determine the symbol of the
nucleus Complete the nuclear
equation
9
Half-Life The half-life of a radioisotope is the
amount of time it takes for one-half of a sample
to decay 20 g 131I 1 half-life 10 g 131I 2
half-lives 5 g 131I
10
Half-Life A decay curve is a diagram of the
decay of a radioactive isotope
11
Sample Problem Phosphorus-32, a radioisotope used
in the treatment of leukemia, has a half-life of
14 days. If a sample contains 8.0 g of
phosphorus-32, how many grams of phosphorus-32
remain after 42 days?
Answer How many half-lives if 42 days? 1.
Write the equality 2. Treat the problem
like any other with a conversion-factor! 3.
Determine how much sample decays and how much
remains.
12
Nuclear Fission Fission is. The process in
which large nuclei are split into smaller pieces,
releasing large amounts of energy 0n 92U
? 36Kr 56Ba 3 0n E Where E
mc2 E Energy Released m mass lost c
speed of light 3 x 108 m/s Chain Reaction is
a fission reaction that will continue once it has
been initiated by a high E neutron bombarding a
heavy nucleus such as U-235
235
142
91
1
1
13
Nuclear Fusion Fusion is a reaction in which
large amounts of energy are released when small
nuclei combine to form larger nuclei This
process occurs continuously in the sun and other
stars, providing us heat and light Requires high
Ts (1 x 109 ºC) to overcome H-H nuclei repulsion

• Great promise for fusion!!!
• Advantageous because
• H2(g) is plentiful as a natural resource
• The waste products of fusion have shorter
  half-lives compared with fission
• Less waste generated by fusion than fission
• Issues to work out

14

• Nuclear Power Plants
• Uranium-235 is used
• Held below critical mass quantities (therefore
  no chain reaction)
• Energy production selectively maintained with
  control rods, which absorb some of the
  fast-moving neutrons
• Heat from fission produces steam
• Steam drives the generator, leading to energy
  production!

• Causes for concern http//www.chernobyl.co.uk/
  
• Safely storing radioactive waste
• Safely transferring radioactive waste to storage
  sights

15
Electricity Energy Supplied in the United States

• Percentages of electric power generation in the
  U.S. in 2003 from various sources.

16
Nuclear Energy

• The U.S. uses much less nuclear energy than many
  developed nations do.

Nuclear power plants produce minimal air
pollution. However, many elaborate and expensive
safety precautions must be employed. Also,
fission products (nuclear waste) must be dealt
with.