why 1 amu is defined as 1/12 of carbon atom?
Answers
Fist of all , what is a.m.u ?
A.M.U is the contracted form of atomic mass unit.
Atomic mass unit is the smallest unit which is used to measure the atomic mass of bigger substances .
Now A.M.U is also defined as 1/12 th of the mass of a single carbon atom .
Carbon atom has an atomic weight of exactly "12.000" g and accurately.
No other element is that much accurate . For example , if you take oxygen , oxygen has 15.999 g which is "approximately" equal to 16 g but not exactly equal.
Even hydrogen has 1.008 g and this is not useful for measuring atomic mass especially if the mass is a whole number .
1/12 th of carbon atom = 1/12 × 12.000 g = 1.00 g
This is used because of its accuracy . The atomic mass unit should be accurate and precise . No other number is better than 1.00 g and hence carbon is chosen and 1/12 th of carbon is chosen .