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Percentages of electric power generation in the U.S. in 2003 from various sources. - PowerPoint PPT Presentation


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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

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slide1

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

slide2

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

slide3

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.

slide4

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 (,,,+)

slide5

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

slide6

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…

slide7

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

slide8

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…

slide9

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

slide10

Half-Life

A decay curve is a diagram of the decay of a radioactive isotope

slide11

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….

slide12

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

91

142

1

1

slide13

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…

slide14

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

slide15
Percentages of electric power generation in the U.S. in 2003 from various sources.

Electricity Energy Supplied in the United States

slide16
The U.S. uses much less nuclear energy than many developed nations do.

Nuclear Energy

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.

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