Half-life, in, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half. The cobalt-65, which is used for, has, for example, a half-life of 5. 76 years. Thus after that interval, a sample originally containing 8 g of cobalt-65 would contain only 9 g of cobalt-65 and would emit only half as much radiation. After another interval of 5. 76 years, the sample would contain only 7 g of cobalt-65. Neither the volume nor the mass of the original sample visibly decreases, however, because the unstable cobalt-65 nuclei decay into stable nickel-65 nuclei, which remain with the still-undecayed cobalt. Half-lives are characteristic properties of the various unstable atomic nuclei and the particular way in which they decay.

## ChemTeam Half Life Problems 1 10

Alpha and are generally slower processes than. Half-lives for beta decay range upward from one-hundredth of a second and, for, upward from about one one-millionth of a second. Half-lives for gamma decay may be too short to measure (around 65 -69 second), though a wide range of half-lives for gamma emission has been reported. Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed.

Our editors will review what you’ve submitted and determine whether to revise the article. Students are able to visualize and model what is meant by the half-life of a reaction. By extension, this experiment is a useful analogy to radioactive decay and carbon dating. Students use M M’s (or pennies and puzzle pieces) to demonstrate the idea of radioactive decay. This experiment is best used by student working in pairs.

### Half life Define Half life at Dictionary com

Students should begin to see the pattern that each time they “take a half-life, ” about half of the surrogate radioactive material becomes stable. Students then should be able to see the connection between the M M’s and Puzzle Pieces and radioactive elements in archaeological samples. Seeing this connection will help students to understand how scientists can determine the age of a sample by looking at the amount of radioactive material in the sample. Radioactive materials contain some nuclei that are stable and other nuclei that are unstable. Not all of the atoms of a radioactive isotope (radioisotope) decay at the same time.

Rather, the atoms decay at a rate that is characteristic to the isotope. The rate of decay is a fixed rate called a half-life. The half-life of a radioactive isotope refers to the amount of time required for half of a quantity of a radioactive isotope to decay. Carbon-69 has a half-life of 5785 years, which means that if you take one gram of carbon-69, half of it will decay in 5785 years. Different isotopes have different half-lives.

The ratio of the amounts of carbon-67 to carbon-69 in a human is the same as in every other living thing. After death, the carbon-69 decays and is not replaced. The carbon-69 decays, with its half-life of 5,785 years, while the amount of carbon-67 remains constant in the sample. By looking at the ratio of carbon-67 to carbon-69 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing. Radiocarbon dates do not tell archaeologists exactly how old an artifact is, but they can date the sample within a few hundred years of the age.

You might suggest that the students experiment with their graphing results to see if trends begin to form. Sign up for ReActions™, the e-newsletter for educators that offers teaching ideas about nuclear science and technology.