Radioactivity

What is radioactivity? The process that occurs when a nucleus becomes unstable and starts to decay. It emits ALPHA, BETA or GAMMA radiation. To be unstable, an isotope has too many or too few neutrons compared to the number of protons

Alpha When alpha radiation occurs an ALPHA particle is emitted from the decaying nucleus. Alpha particles: Contains 2 protons and 2 neutrons Is the same as the nucleus of a helium atom. Has a charge of +2 Has an Atomic mass of 4 Its symbol is the same as the symbol of a helium nucleus

Beta When a neutron decays into a proton and emits an electron. The electron emitted from the nucleus is the BETA particle. Beta decay is caused by weak force Because the atom is gaining a proton, the atom undergoes transmutation, changing one element to another through nuclear decay

Gamma Rays electromagnetic waves have no mass, no charge and travel at the speed of light Are emitted when alpha or beta decay occur

What happens with each? ALPHA BETA GAMMA

List the types of radiation from most to least penetrating and explain

Half-Life the rate at which radioactive isotopes decay varies from element to element. some isotopes decay rapidly (within a few milliseconds), while others take millions of years to decay.

Half-Life half-life = amount of time it takes for half the nuclei in a sample of the isotope to decay. the isotope that is produced by the decay process is called the daughter nucleus. a “T-chart” can be used to help determine how much of the original nucleus is left after a certain number of half-lives have passed. the isotopic notation and given mass of the radioactive element goes on top of the T-chart. the left-hand side of the T-chart is filled in with the increments of time that pass after each half-life.

Let’s Try It! the right-hand side can be filled in with either: the percent of the original isotope left after each half-life passes, or the mass of the isotope left after each half-life passes. let’s try filling in a T-chart for the problem in the box below: Let’s Try It! Ex1: Carbon-14 has a half-life of 5,730 years. How much of a 144 g sample of carbon-14 will remain after 5 half- lives have passed?

Let’s Try It! let’s try filling in a T-chart for the problem in the box below: as you can see, the time increment is added on each time a half-life passes (left). the mass remaining is divided by 2 each time a half-life passes (right). eventually, there will be so little of the original isotope left, that it is too small to measure. carbon 14 144 Ex1: Carbon-14 has a half-life of 5,730 years. How much of a 144 g sample of carbon-14 will remain after 5 half-lives have passed? 72 11,460 36 17,190 18 22,920 9 28,650 4.5 g

I-131 (50.00 g) Na-24 (208 g) 8.10 25 15 104 16.2 12.5 30 52 45 26 24.3 6.25 60 13 24.3 days 15 hours Radioactive Dating the age of rocks and fossils can be measured based on a ratio of the amount of radioactive nuclei that remain undecayed vs. the amount of daughter nuclei produced. geologists, archeologists, and biologists use that information to calculate the amount of half-lives that have gone by since the sample started decaying. by adding up the number of half-lives that have passed, the scientists can determine an approximate age range for how old an object is.