Kilogram is not
a very convenient unit to measure such small quantities Therefore, a
Chapter Thirteen
NUCLEI
Rationalised 2023-24
307
Nuclei
different mass unit is used for expressing atomic masses This unit is the
atomic mass unit (u), defined as 1/12th of the mass of the carbon (12C)
atom According to this definition
 mass of one 12
C atom
1u = 
12
     
26
1