Potassium argon dating formula
The total mass of the argon in the Earth's atmosphere is (total mass of atmosphere) x 1.3% = (5.1 x 10 kg argon in the atmosphere Thus, the amount of argon in the atmosphere is about 1.4% of the amount of argon-40 produced in the Earth's crust over the past 4.5 billion years.
Most of the argon produced in the crust remains locked in the rock.
Therefore, the amount of argon-40 produced by the decay of potassium-40 is 11% of the total mass of potassium that has decayed: 4.2 x 10 kg of argon-40 produced in the Earth's crust Argon is a common gas, making up 0.9% by volume or 1.3% by mass of the atmosphere.
Only nitrogen and oxygen (and sometimes water vapor, depending on the humidity) are more plentiful in the atmosphere.
The potassium-argon dating method has been used to measure a wide variety of ages.
The standard form of the periodic table shown here includes periods (shown horizontally) and groups (shown vertically).Your answers might be slightly different due to rounding.The decay of potassium-40 to argon-40 explains why there is so much argon in the atmosphere, compared with the other noble gases.Almost all atmospheric argon (99.6%) is argon-40, whereas the argon in the Sun and stars, produced by stellar nucleosynthesis, is mostly argon-36.This suggests that primordial argon is in the form of argon-36 and essentially all of the argon in the atmosphere was produced by the decay of potassium-40 to argon-40.
Here is a typical rock dating problem: Question: A rock sample is found to contain 1.00 gram of potassium and 6.0 micrograms of argon. Answer: At the present time, all natural potassium is 0.012% potassium-40.