Question

are mass number and atomic mass of an element equal in all respects.

Answer 1

No
Atomic mass is the mass of an element
Mass number is also the same but chemically they won't be same

Answer 2

Answer:

While the mass number is the sum of the protons and neutrons in an atom, the atomic number is only the number of protons. The atomic number is the value found associated with an element on the periodic table because it is the key to the element's identity. The only time the atomic number and mass number are the same is when you are dealing with the protium isotope of hydrogen, which consists of a single proton. When considering elements in general, remember the atomic number never changes, but because there may be multiple isotopes, the mass number may change.