Is there radon in your basement?

http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg

Isotopes

• Atoms of a given element with:

same #protons

but

different # neutrons

Isotopes of Carbon

• Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus.

• Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film.

• His associates were Marie and Pierre Curie.

Radioactive Isotopes

Marie Curie a Pioneer of Radioactivity

• Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie.

• Winner of the sole 1911 Nobel Prize for Chemistry.

3 Main Types of Radioactive Decay

• Alpha a

• Beta b

• Gamma g

• So, which form of radiation is the most penetrating?

• Alpha Beta or Gamma?

Radioactive Half-Life (t1/2 ):

• The time for half of the radioactive nuclei in a given sample to undergo decay.

Common Radioactive Isotopes

Isotope Half-Life Radiation Emitted

Carbon-14 5,730 years , b g

Radon-222 3.8 days a

Uranium-235 7.0 x 108 years , a g

Uranium-238 4.46 x 109 years a

Radioactive Half-Life

• After one half life there is 1/2 of original sample left.

• After two half-lives, there will be

1/2 of the 1/2 = 1/4 the original sample.

After three half lives, there will be _______ of the original sample left?

Example

You have 100 g of radioactive C-14. The half-life of C-14 is 5730 years.

• How many grams are left after one half-life? Answer:____________

• How many grams are left after two half-lives?_______

. The half life of Zn-71 is 2.4 minutes. If we had 100 grams at the beginning, how many grams would be left after 7.2 minutes elapsed? SHOW SET UP

2. Os-182 has a half life of 3.6 days. How many grams of a 10.0 gram sample would have decayed after exactly three half lives? SHOW SET UP

. 200.0 grams of an isotope with a half life of 36.0 hours is present at time 0. How much time in hours will have elapsed when 12.5. grams remain? SHOW SET UP

Rule of 10?

• It takes approximately 10 half lives to for a radioactive material to decay to a “safe” level.

President Zachary Taylor and the Laboratory:Presidential Visit from the GraveShortly after breaking ground for the Washington Monument on July 4, 1850, President Zachary Taylor, a hero of the Mexican War, fell ill. When he died suddenly a few days later, the cause was listed as gastroenteritis--inflammation of the stomach and intestines.Some historians suspected that Taylor's death may have had other causes, and in 1991 one convinced Taylor's descendants that the president might have suffered arsenic poisoning. As a result, Taylor's remains were exhumed from a cemetery in Louisville and Kentucky's medical examiner brought samples of hair and fingernail tissue to Oak Ridge National Laboratory for study.In the Chemical and Analytical Sciences Division, Larry Robinson and Frank Dyer headed the Taylor investigation, using neutron activation analysis to measure the amount of arsenic in the hair and nail samples. After placing the samples in a beam of neutrons from the High Flux Isotope Reactor, Dyer and Robinson looked at the gamma rays coming from the samples for the distinctive energy levels associated with the presence of arsenic. Arsenic is among the easier elements to identify through neutron activation and can be detected in a few parts per million. Most human bodies contain traces of arsenic, so the essential issue in the Taylor case was whether the samples from Taylor contained more arsenic than would be normal after 141 years in the crypt.Working late in the evenings, Dyer and Robinson in a few days calculated the arsenic levels in the samples and sent them to the Kentucky medical examiner for his decision. After reviewing the test results, the examiner announced that the arsenic levels in the samples were several hundred times less than they would have been if the president had been poisoned with arsenic. This finding acquitted several of Taylor's prominent contemporaries of the suspicion of murder and proved that history and science share a common quest for truth.