Apotassium-40 sample starts with 50 atoms, and 1.25 billion years later, there are 25 atoms. what is the half life of potassium-40?

a. 25 years
b. 40 years
c. 1.25 years
d. 2.5 years

Potassium-40 has a half life of 1.25 billion years.

New amount = Original amount × (1/2)^n ; where n is the number of half lives.

Original amount is 50 atoms

New amount is 25 atoms

Therefore;

25 = 50 × (1/2)^n

1/2  = (1/2)^n

Thus; n = 1

n = 1 which is equivalent to 1.25 billion years

Therefore;

Potassium-40 has a half life of 1.25 billion years.

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explanation:

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.