1. The Atomic Nucleus--Natural Radioactivity
Most elements have one or more isotopes with
unstable nuclei
An unstable nucleus is radioactive
Radioactive nuclei spontaneously decay & emit radiation

2. Transmutation
Radioactive Decay frequently results in a change in the number of protons in a nucleus
The identity of the element changes!

3. Types of Radiation Alpha Particles () mass number = 4
charge = +2
Beta particles ()
mass number = 0
charge = -1
Gamma rays()
energy

4. Change in the Nucleus:

5. Alpha particle Beta particle Gamma ray
Type of Radiation Symbol Change in Nucleus Mass # Charge
Alpha particle
Beta particle
Gamma ray

6. Creates ions or free radicals (chemically reactive)
Ionizing Radiation = radiation that liberates particles that have enough energy to remove an electron from an atom or molecule
Creates ions or free radicals (chemically reactive)
Rapidly dividing cells are most sensitive
Type of Radiation travel distance (air) (tissue depth) shielding
Alpha particle
Beta particle
Gamma ray

7. Writing an Equation for Alpha Decay:
U-238 decays to give Th-234 and an alpha particle.

8. Writing an Equation for Alpha Decay:
Americium-241 undergoes alpha decay.

9. Writing an Equation for Beta Decay:
The beta decay of a carbon-14 nucleus produces a nitrogen-14 nucleus.

10. Writing an Equation for Beta Decay:
Cobalt-60 is a synthetic isotope with a half-life of 5.27 years.
When Cobalt-60 decays, both a -particle and -rays are emitted.

11. Writing an Equation for Gamma Emission:
pure gamma emitters are rare
gamma emission frequently accompanies  and  radiation
Technitium-99m is a radioisotope used in nuclear medicine. It must be produced in a radiology lab and
used quickly (t1/2 = 6 hours).

12. Half-Life of Radioisotopes
Half-life = the time it takes for one-half of a sample to decay

13. Strontium-90 released by testing of nuclear weapons/nuclear accidents
chemically similar to Calcium (bones, teeth, milk)
half-life = 28.8 years
decays by beta emission
Write an equation:
For every 100 gram of Sr-90 released by the Chernobyl nuclear reactor meltdown in 1986, approximately how many grams remain?

14. Radioactive tracers are used in Medical Imaging:
Iodine-123 is a radioisotope used to assess Thyroid activity (t1/2 = 13 hours)
Phosphorus-32 is used to identify malignant tumors
(cancer cells tend to accumulate more P)