What causes an atom to be radioactive?

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What causes an atom to be radioactive?

• When the strong force is not large enough to keep
  the entire nucleus together the atom is
  considered radioactive.
• Large nuclei tend to be more reactive. Any
  nuclei with more than 83 protons is considered
  radioactive.
• The Actinide series (bottom row) is made up of
  almost all radioactive elements

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What causes an atom to be radioactive? (cont)

• The ratio of neutrons to protons affects the
  stability of a nucleus
• Lighter atoms have about a 11 ratio
• Heavier atoms have about a 32 ratio
• In general, atoms with too many or too few
  neutrons compared to protons are considered
  radioactive

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Radioactivity

• Some elements will change (decay) into another
  element.
• Ex Radon gas turns into lead.
• These elements are called
• RADIOACTIVE
• When these elements decay their nucleus
• changes into another element and they give off
• RADIATION.

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What do we mean by Radioactivity?
Radioactive decay is the process in which an
unstable atomic nucleus loses energy by emitting
radiation in the form of particles or
electromagnetic waves. There are numerous types
of radioactive decay. The general idea An
unstable nucleus releases energy to become more
stable
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3 Types of Radiation
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• Alpha Decay ( a )
• Made of 2 protons and 2 neutrons (like a helium
  atom with a 2 charge)
• The original atom loses 2 protons so becomes a
  new element
• Weakest can be stopped by a piece of paper.

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Beta Decay ( ß )

• A neutron has decayed into a proton and electron,
  the electron is emitted
• The original has an added proton so becomes a new
  element, or undergoes transmutation (mass stays
  the same)
• 2nd strongest can be stopped by aluminum foil.

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Gamma Rays ( ? )

• No mass or charge and travel at the speed of
  light
• Usually emitted when alpha or beta decay occurs
• Stopped by 5 cm of lead.

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Radioactivity Song

• https//www.youtube.com/watch?vIjZe6xSTWhM

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• Example
• You have 8 mms. If the half-life of mms
• is 1 minute, how many will be left after 3
• minutes?
• Number of mms Time
• 8 0
• 4 1
• 2 2
• 1 3

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• Example
• If you had 100g of a radioactive substance
• that has a half-life of 4 days, how much
• would be left after 8 days?
• Radioactive substance Days
• 100g 0
• 50g 4
• 25g 8

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• Example
• If you had 1000g of a radioactive substance
• that has a half-life of 25 years, how much
• would be left after 100 years?
• Radioactive substance Years
• 1000g 0
• 500g 25
• 250g 50
• 125g 75
• 62.5g 100

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• Each radioactive element has a certain
• HALF LIFE.
• Half Life
• The amount of time it takes for half of the
  element to decay (change).

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Fusion/Fission Video

• https//www.youtube.com/watch?voIe1EDExxyg

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Fusion
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Fission
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Chain Reaction Lab

• After completing the procedures complete the
  following in your science notebook
• A diagram of a controlled reaction
• A diagram of an uncontrolled reaction
• What does it mean if the critical mass has been
  reached with the dominoes? What would this mean
  in a nuclear reaction?