Download Chapter 19 Radioactive Material An Isotope is an element with a

Chapter 19 Radioactive Material An Isotope is an element with a different atomic masses from molecule to molecule due to a difference in the number of neutrons. When an Isotope is Radioactive it is produces a decay mechanism. Common radioactive isotopes are found in Uranium, Carbon, Polonium, Radon, and Plutonium Nuclide-­‐ consists of the protons and neutrons in the nucleus As the atomic mass of the elements increase, so does the number of isotopes the element can have. This is due to the increase of the size of the nucleus, because the larger the nucleus the more neutrons it can hold. Radioactive Decay Natural decay 1 neutron= 1 proton+1 electron There are 3 types 1. Alpha (α) when Helium 4 is produced, very common in heavy radioactive metals particle: 24𝐻𝑒 Ex: 88222𝑅𝑎  24𝐻𝑒 +86218𝑅𝑛+ 00ɣ 2. Beta (β) when a neutron is split, producing a proton and an electron. Note that no mass is added to the element, but a neutron is converted into a proton. Particle: −10𝑒 𝐸 𝑥 :614𝐶  714𝑁+ −10𝑒+00ɣ 3. Gama (ɣ) a photon of light, results in no change in both the mass and atomic number. Produced during alpha, beta, and electron capture. Particle: 00ɣ Ex: excited nucleus ground-­‐state nucleus + 00ɣ 4. Positron (+e) has the same mass of an electron, but a different charge. When a positron is produced, a proton is changed to a neutron but no mass is added to the element. Ex: sodium-­‐ 22 1122Na 10e + 1022Ne 5. Electron Capture: when one of the inner orbital electrons is pulled into the nucleus. Causes no change in mass number but a decrease in the atomic number. Does not happen very often. Particle -­‐10e Ex: 80201Hg + -­‐10e79201Au + 00ɣ Usually, 1 isotope will go through many different decays in order to produce a stable isotope. This is called a decay series. Ex: U-­‐235 (decay series) Pb-­‐207 Transmutation: when 1 element converts into another element. This can happed through radioactive decay. 2 Types: 1. Natural-­‐ occurs naturally in nature Ex: carbon 14 to nitrogen 14 2. Artificial-­‐ occurs by fission, or the process of splitting an atom, which releases energy that can then be used for nuclear energy or nuclear bombs. Half Life is when ½ of the material has decayed. This happens at a different pace for all elements. The equation for measuring ½ life is: Mass (final)/Mass (initial)= (½)(elapse of time/half life) Analytical Techniques to determine is something is radioactive: many substances take a very long time to decay, so scientist made devices to determine wheter a substance is radioactive. They are: -­‐Scintilator Comter -­‐Geiger Comter (α particles) -­‐Radiation Badges-­‐ worn by people who are exposed to radiation everyday, the badge will turn red if the level of radiation becomes unsafe. Radioactive dating-­‐ estimating the age of an object based upon the % of radioactive Isotope found in the object. Medical uses: Tracers-­‐ used to identify a problem, often in a person’s body, by having the person ingests the radioactive isotope and then tracing that isotope in the person’s circulator system. Chemotherapy-­‐ using radiation to kill cancerous cells in a person’s body Nuclear Energy: -­‐Fission-­‐ the process of splitting an atom to release energy. A neutron strikes radioactive isotope causing it to split. Uranium atoms are spilt to produce electricity at a nuclear power plant. Once one atom splits, it causes a cascade effect, making more and more atoms split. This means that the reaction starts off small and then becomes bigger and bigger. To harness this energy, the uranium rods are placed in side water, which gets hot when the uranium atoms split. The hot water turns into steam which then spins a turbine that is hooked u to a generator. To prevent the uranium from creating to much heat that might melt the walls of the reactor, carbon rods deflect neutrons from hitting uranium atoms, which slows down the cascade effect, producing less heat. Fusion-­‐ The process of combining 2 atoms. This process only happens on stars with hydrogen and helium atoms. This is how the sun is able to warm the earth from so far away. Fusion creates much more energy then fission does but has not been possible to replicate on the earth due to the tremendous amount of heat fusion creates. The gas formed by the fusion of hydrogen would not be able to be stored anywhere on earth. Scientists are still trying to figure out a way to do fusion on earth. Ex: 11H(deuterium) 12H +10e (positron) (deuterium) 12H+ 11H 23He +γ 23He + 23He 24He+10e +γ When the 11H runs out in a star, it expands (super nova), and then collapses in on it self. Carbon Dating (carbon -­14 dating) This technique can be used to date human and animal remains. Carbon -­‐14 dating relies on the beta decay of the radioactive isotope of carbon-­‐14 to nitrogen-­‐ 14. Carbon-­‐14 is continuously made in the atmosphere, so the process of decay and production balance each other out. However, when an animal or plant dies, it stops taking in carbon-­‐14 so the carbon-­‐14 left in the animal or plant begins to decay into nitrogen-­‐14. Carbon-­‐ 14 has a half-­‐life of 5730 years, so by comparing the amount of carbon-­‐14 in the atmosphere normally to the amount in the specimen one can determine the approximate age of the specimen.