The decay of radioactive elements occurs at a fixed rate. The half-life of a radioisotope is the time required for one half of the amount of unstable material to degrade into a more stable material. The half-life of Carbon-14 is 5,730 years. Choose ALL the true statements regarding the Carbon-14 isotope. A) 100 grams of C-14 decays to 25 grams in 11,460 years. B) The C-14 isotope is only useful for dating fossils up to about 50,000 years old. C) A sample contained 3,360 atoms of C-14. 8 half-lives passed and 210 C-14 atoms remained. D) If an ancient bone contains 6.25% of its original carbon, then the bone must be 22,920 years old. E) A sample of 4,000 radioactive C-14 atoms undergoes decay. After 5 half-lives there are 800 radioactive atoms remaining.

100 grams of C-14 decays to 25 grams in 11,460 years.

The C-14 isotope is only useful for dating fossils up to about 50,000 years old

If an ancient bone contains 6.25% of its original carbon, then the bone must be 22,920 years old.

Explanation:

We already know that the half life of C-14 is 5,730 years. After the first half life, we have 50 grams remaining. This takes 5,730 years. After the second half life (11,460 years now gone) we have 25 grams of C-14  left.

If a fossil material is  older than 50,000 years an undetectable amount of 14C is left in the sample hence Carbon-14 is no longer suitable for dating the sample.

From;

0.693/5730 = 2.303/t log (No/0.0625No)

Where;

t = time taken and No = initial amount of C-14

0.693/5730= 2.77/t

t = 22,920 years

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be

your answer is c) plasma

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