How long will it take for a quarter of the uranium 238 atoms in a rock to decay to lead 206?

about 4.5 billion years
Radiometric Dating Some examples: the half-life for the decay of potassium 40 atoms into argon 40 atoms is about 1.3 billion years, the half-life for the decay of uranium 238 into lead 206 is about 4.5 billion years, and the half-life for the decay of carbon 14 into Nitrogen 14 is 5730 years.

What is the age of rock if it contains uranium 238?

The half – life of U 238 is about 4.5 billion years.

What of U 238 will remain after three half-lives?

13.5 billion years
Explanation: The mass of Uranium halves every 4.5 billion years, so 13.5 billion years= 3 half-lives.

How was the half-life of uranium 238 determined?

The half-life is then determined from the fundamental definition of activity as the product of the radionuclide decay constant, λ, and the number of radioactive atoms present, N. A = 1014 cpm/0.315 c d-1 = 3219 dpm = λ N = (ln2/T1/2)(4.41 x 10-3 g/238.03 g/g-atomic weight)(6.022 x 1023 atoms/g-atomic weight).

How old would a sample with 50\% uranium-238 and 50\% lead-206 be?

After a second half-life, the 50 gm of U-238 would drop to 25 while the 50 gm of Pb-206 would increase to 75. Thus, two half lives. Since the half-life of U-238 is 4.5 Billion years, this rock must be 9 BY old. 1d.

How is the half-life of a radioactive isotope determined?

One important measure of the rate at which a radioactive substance decays is called half-life, or t1/2. Half-life is the amount of time needed for one half of a given quantity of a substance to decay. By measuring the decay of a sample of barium-137, you will be able to calculate its half-life.

What is the half-life of uranium-238 quizlet?

Uranium-238 has a half-life of 4.5 billion years.

How old is a rock sample that contains uranium-235 and lead-207 in equal amounts?

704 million years
RADIOMETRIC TIME SCALE