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Lab 525 ONLINE LESSON. If viewing this lesson in Powerpoint Use down or up arrows to navigate. Do take notes as we peruse through this lesson…. Radiometric Dating. A question that is often asked… How old is the earth?. And the answer is…. Pretty Old.
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If viewing this lesson in Powerpoint Use down or up arrows to navigate
Radiometric dating is the process of measuring the age of rocks
By measuring the age of rocks, geologists can determine the age of a number of geologic events...
Radiometric dating is based on the concept of radioactivity…the disintegration (falling apart) of atoms
An atom is the smallest particle in the universe with a distinct set of chemical characteristics…..
ATOM PROTON (positively charged) P NEUTRON (neutral) N ELECTRON (negatively charged) e-
The electron orbits the nucleus which contains the protons and neutrons e- NUCLEUS
RULE: The number of protons determines the chemical identity of an element
For instance… -all Hydrogen contains 1 proton… -all Helium contains 2 protons… -all Uranium contains 92 protons…
Element = a substance that cannot be broken down into other substances by chemical means…
For instance… Hydrogen is an element Helium is an element Uranium is an element
Carbon-12 is a species of carbon… CARBON 12C
It contains 6 protons and 6 neutrons…for a total of 12 particles in the nucleus CARBON 12C
Carbon-14 is another species of carbon… CARBON 14C
Carbon-14 contains 6 protons but 8 neutrons…for a total of 14 particles… CARBON 14C
The neutron count may vary but the proton count remains the same…6 protons… CARBON 14C
SO: The number of protons determines the chemical identity of an element
Decay types are part of Radioactivity …there are three types to be concerned with…
DECAY TYPES ALPHA P P N N e- BETA N P ELECTRON CAPTURE P N e-
DECAY TYPES ALPHA P P N N 2 protons and 2 neutrons are thrown out of the nucleus…this reduces the number of protons and thus changes the element…
DECAY TYPES A neutron turns into a proton e- BETA N P This will change the element
DECAY TYPES A proton turns into a neutron This will change the element ELECTRON CAPTURE P N e-
With all 3 decay types…elements will change their chemical identity because of the change in the number of protons…
A common decay series is 238U/206Pb URANIUM = PARENT LEAD = DAUGHTER
A decay series is the progression of the disintegration of elements…a start to finish process…
This beginning to end process is the essence of radiometric dating…
For instance… Uranium 238 is a parent element and it decays over time to to Lead 206… 238U92
The decay process starts out with 92 protons and 146 neutrons for a total of 238 particles in the nucleus… 238U92
And includes a series of steps before uranium turns into lead… 238U92
2 protons and 2 neutrons are ejected from the nucleus and changes the element… uranium to thorium 238U92
A neutron is converted to a proton and changes thorium to paladium… 234Th90
And so on and so on… 234Pa91