Question

Carbon - 12 atom (isotope of carbon) was later in 1961 considered
the standard for comparison of mass of other atoms or molecules.
Why?​

Answer 1

Answer:

Explanation:

First of all, relative atomic mass, means that what is the atomic weight of any atom compared to atomic weight of carbon atom. Or we can say how many times any atom is heavier then 1/12 mass of carbon.

Now, question arrises that why only carbon?

=> because atomic weight of carbon is 12 and also, no. of proton and neutron were also 6 each which sums up to 12. So it was concluded that carbon will be the best atom for comparison of atomic masses of other elements' atom as it had exactly 12 atomic mass. Surely carbon, has an isotope with atomic mass 14. So you may wonder then what's the point if the average atomic mass of carbon is not exactly 12?

Well, the thing is that the other isotope of carbon is not that common in the atmosphere or hydrosphere or troposphere or etc. It's found in tree barks and other objects which are really old enough that too, in very small amounts. C-14 is radioactive and hence is also useful for calculating the age of a material (carbon dating). And also, may I remind you that carbon 12 is used to calculate relative atomic mass. The average atomic mass of carbon isn't considered for calculating it.

Earlier it was thought that hydrogen should be compared with other elements as it had atomic mass 1, but it had three isotopes kind of abundant on Earth which made its average atomic mass not equal to exactly 1. And neither of any isotope has integer value mass. Oxygen was also considered along with hydrogen for comparison as it reacted with a large no. of elements and so there were two atomic mass tables one with carbon and other with oxygen, but later when isotope of oxygen was found too, and only one table was to be selected, the table with carbon-12 was chosen.

LATIN NAME : CARBONIUM

ENGLISH NAME;carbon

year discovered;1791

DISCOVERED BY;HUMPHRY DAVY

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