If a rock was determined to be around 3.9 billion years old how much Potassium 40 would be left in that rock sample? (Percentage of Potassium 10

the answer is false because not all countries have geysers under their crust. for example, iceland uses geothermal energy because it is available every in their country.  

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.

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