Scientists unearthed an ancient scroll for determining the age of a fossil. The process involved collecting 6C14 from the fossil and comparing it with a fresh sample. Scientist found that the ratio of 6C14 : 6C12 decreased as compared to the fresh sample.
(a) Name the process.
(b) 6C14 and 6C12 are collectively known as ...............
(c) Why did the ratio decrease in the fossil?
(d) Complete the equation by filling the blanks:
...............X............... + 0n1 ⟶ 6C14 + 1P1
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(a) The process is called carbon dating.
(b) 6C14 and 6C12 are collectively known as isotopes (of carbon).
(c) 6C14 is radioactive and it goes on decaying into nitrogen by the emission of β-particles, while 6C12 is stable and its amount does not change.
While the organism is alive, it keeps taking in carbon from its surroundings, so the ratio 6C14 : 6C12 in it remains the same as in a fresh sample. After its death this intake stops, so the 6C14 present in it goes on decreasing due to decay while the 6C12 remains unchanged. Hence in the fossil the ratio 6C14 : 6C12 is less than that in a fresh sample.
(d) In a nuclear reaction, the mass number and the atomic number are conserved on both sides.
Let the atomic number of X be Z and its mass number be A.
Equating the mass numbers :
A + 1 = 14 + 1
⇒ A = 14
Equating the atomic numbers :
Z + 0 = 6 + 1
⇒ Z = 7
The element with atomic number 7 is nitrogen (N).
Hence, the complete equation is 7N14 + 0n1 ⟶ 6C14 + 1P1.