Radioactive Decay Lab Report
All kinds of rocks contain very small amounts of radioactive elements, these are unstable and they break down into more stable atoms over time, which is called radioactive decay. Scientists can tell how old a rock is by using radiometric clocks, or by looking at its absolute age. Geologists measure the amount of certain radioactive elements; as time passes the radioactive elements change at regular rates, into non-radioactive elements. The older a rock is the larger the number of elements. The age of the rock is found by measuring when the element decays.
Radio isotopes which are used to calculate the age of rocks have very long half-lifes, one of the most commonly used isotopes for this is uranium 238.
Uranium 238: Half life = 4.5 billion years …show more content…
Uranium-238 has half the atoms in any sample will decay in that amount of time.
Uranium-238 decays by alpha emission into thorium-234, which itself decays by beta emission to protactinium-234The various decay products is a a series starting at uranium-238. After several more alpha and beta decays, the series ends with the stable isotope lead-206.
Since scientists know the rate at which uranium 238 becomes lead 206, they can determine the age of a rock that contains uranium 238 from the ratio of uranium 238 to lead 206 in the rock. They can calculate the age more accurately by measuring all the products in the series.
The two uranium-lead dates obtained from U-235 and U-238 have different half-lives, so if the date obtained from the two decays are in agreement, this adds confidence to the date. They are not always the same, so some uncertainties arise in these processes.
Uranium 235: Half life = 700 million
years
The isotope U-235 is important because under certain conditions it can readily be split, yielding a lot of energy. It is therefore said to be 'fissile' and we use the expression 'nuclear fission'.
U 235 decays very slowly, its half-life being about the same as the age of the Earth This means that it is barely radioactive, less so than many other isotopes in rocks and sand.
Unstable radioactive isotopes of elements, such as Uranium-235, decay at constant, known rates over time (its half-life, which is over 700 million years). An accurate estimate of the rock's age can be determined by examining the ratios of the remaining radioactive element and its daughters.
Thorium 232: Half life = 14 billion years
Thorium (is a naturally-occurring radioactive metal found at very low levels in rocks. It has several different isotopes, all of which are radioactive.
Minerals that contain elements can be dated by three separate methods based on the decay of thorium-232 to lead-208. The three dates agree with each other only when no atoms of uranium, thorium, lead, and of the intermediate daughters have escaped.
Rubidium 87: Half life= 48.8 billion years
Rubidium 87 has been used extensively in dating rocks; 87Rb decays to stable strontium-87 by emission of a negative beta particle.
It is a fairly common element, and containing its minerals are found in many rocks. Therefore the use of rubidium-strontium method of measuring time in many cases it is very convenient.
Radio isotopes which are used to calculate the age of rocks have very long half-lifes, one of the most commonly used isotopes for this is uranium 238.
Uranium 238: Half life = 4.5 billion years …show more content…
Uranium-238 has half the atoms in any sample will decay in that amount of time.
Uranium-238 decays by alpha emission into thorium-234, which itself decays by beta emission to protactinium-234The various decay products is a a series starting at uranium-238. After several more alpha and beta decays, the series ends with the stable isotope lead-206.
Since scientists know the rate at which uranium 238 becomes lead 206, they can determine the age of a rock that contains uranium 238 from the ratio of uranium 238 to lead 206 in the rock. They can calculate the age more accurately by measuring all the products in the series.
The two uranium-lead dates obtained from U-235 and U-238 have different half-lives, so if the date obtained from the two decays are in agreement, this adds confidence to the date. They are not always the same, so some uncertainties arise in these processes.
Uranium 235: Half life = 700 million
years
The isotope U-235 is important because under certain conditions it can readily be split, yielding a lot of energy. It is therefore said to be 'fissile' and we use the expression 'nuclear fission'.
U 235 decays very slowly, its half-life being about the same as the age of the Earth This means that it is barely radioactive, less so than many other isotopes in rocks and sand.
Unstable radioactive isotopes of elements, such as Uranium-235, decay at constant, known rates over time (its half-life, which is over 700 million years). An accurate estimate of the rock's age can be determined by examining the ratios of the remaining radioactive element and its daughters.
Thorium 232: Half life = 14 billion years
Thorium (is a naturally-occurring radioactive metal found at very low levels in rocks. It has several different isotopes, all of which are radioactive.
Minerals that contain elements can be dated by three separate methods based on the decay of thorium-232 to lead-208. The three dates agree with each other only when no atoms of uranium, thorium, lead, and of the intermediate daughters have escaped.
Rubidium 87: Half life= 48.8 billion years
Rubidium 87 has been used extensively in dating rocks; 87Rb decays to stable strontium-87 by emission of a negative beta particle.
It is a fairly common element, and containing its minerals are found in many rocks. Therefore the use of rubidium-strontium method of measuring time in many cases it is very convenient.