Question

what is the difference between mass of 1 atom and atomic mass

Answer 1

the atomic mass is the mass of an atomic particle, sub-atomic particle or molecule.
mass of 1 atom = 1.67377 x 10*(-27)

Answer 2

atomic mass is the sum of atomic particle and subatomic .
and,
mass of 1 atom = 6.022*10²³ 
    i hope it helps............