CK-12 Physical Science - For Middle School

http://www.ck12.org Chapter 11. Nuclear Chemistry

MEDIA

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URL: http://www.ck12.org/flx/render/embeddedobject/5014

FIGURE 11.5

This machine scans a patient’s body and

detects radiation.

Lesson Summary

• Radioactivity is the ability of an atom to emit radiation in the form of charged particles and energy from the
  nucleus. Many elements have one or more radioactive isotopes. Elements with more than 83 protons have
  only radioactive isotopes.


• Harmless background radiation comes from radioactive elements in rocks and from cosmic rays. Other sources
  of radiation, such as radon, are harmful. They may cause illness in living things and damage materials such as
  metals. Radiation has several uses, including detecting and treating cancer.

Lesson Review Questions

Recall

1. Define radioactivity.


2. What is radiation?


3. Describe how radioactivity was discovered.


4. What is background radiation? Where does it come from?


5. Why is radiation harmful to both living and nonliving things?


6. Identify three uses of radiation.