Question

How can you define Relative atomic mass unit, and why do we compare it with C-12

Answer 1

@Callisto

Answer 2

As I remember, it's because it's a very abandon and very stable element.

Answer 3

You can find it in living things...

Answer 4

okay and the formula = R.A.M = average mass of an atom of an element/mass of c-12 isotope * 1/12

can u give me an example and show how this works?

Answer 5

Perhaps this site can help a little.
http://www.avogadro.co.uk/definitions/ar.htm

Answer 6

thanks :)

Answer 7

Welcome.

Answer 8

Of the elements in the first three periods, only Si and C can be easily prepared as very pure unreactive solid samples under normal conditions. Carbon has only two naturally occuring isotopes, C-12 and C-13, and that means to prepare pure carbon-12 you can make use of an 8.3% mass difference. Silicon has four naturally occuring isotopes, and Si-29 differs by only 3.6% from the most common isotope, Si-28. Harder to separate.

However, I vaguely recall hearing people argue that Si might be a better standard, because techniques to prepare extremely pure Si have become available through development in the microchip industry.

Answer 9

well well... it's C-14 I believe?!
Somehow, I think C is chosen because it can be easily obtained. Not sure of this point.

Answer 10

well how bout that