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Chapter 7 - Radioactivity

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Chapter 7 - Radioactivity Science 10 7.1 Atomic Theory and Radioactive Decay Natural background radiation exists all around us. Radioactivity is the release of high ... – PowerPoint PPT presentation

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Title: Chapter 7 - Radioactivity


1
Chapter 7 - Radioactivity
  • Science 10

2
7.1 Atomic Theory and Radioactive Decay
  • Natural background radiation exists all around
    us.
  • Radioactivity is the release of high energy
    particles or waves.
  • We use radioactive materials for many things
  • X-rays, radiation therapy and electricity
    generation are beneficial.
  • High energy particles and waves can do damage to
    DNA in our cells.
  • When atoms lose high energy particles and waves,
    ions or even new atoms can be formed.
  • High energy waves and particles are called
    radiation when they leave the atom.

3
The Electromagnetic Spectrum
4
Some History
  • Radiation is everywhere, but can be difficult to
    detect.
  • Roentgen named X-rays with an X 100 years ago
    because they were previously unknown.
  • Becquerel realized uranium emitted seemingly
    invisible energy.

5
  • Marie Curie and her husband Pierre named the
    energy radioactivity.
  • Early discoveries of radiation relied on
    photographic equipment
  • Later, more sophisticated devices such as the
    Geiger-Müller counter were developed to more
    precisely measure radioactivity.

Radium salts, after being placed on a
photographic plate, leave behind the dark traces
of radiation.
6
Isotopes
  • are different atoms of the same element, with a
    different number of neutrons in the nucleus.
  • Changing the of neutrons changes the mass
    number
  • Remember mass protons neutrons
  • isotopes still have the same
  • number of protons / atomic number
  • element symbol

7
Atomic Mass (the decimal s)
  • Atomic mass average of the mass numbers for all
    isotopes of an element.
  • If 19.9 of boron atoms have 5 neutrons, 80.1
    have 6 neutrons
  • 19.9 have a mass number of 10, and 80.1 have a
    mass number of 11
  • (.199 10) (.80111) 10.8
  • atomic mass of boron 10.8

8
Representing Isotopes
  • Isotopes are written using standard atomic
    notation.
  • Chemical symbol atomic number mass number.
  • Potassium has three isotopes,

9
  • Potassium is found in nature in a certain ratio
    of isotopes
  • 93.2 is potassium-39
  • 1.0 is potassium-40
  • 6.7 is potassium-41
  • Atomic mass
  • (.932 x 39) (.001 x 40) (.067 x 41)
  • 39.1
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