How Atomic number is a more fundamental property of an element than its atomic mass?

Explanation

(i) The a tomi c number of an element indicates the number of protons in the nucleus or the number of electrons in the atom .
(ii) All the atoms of an element have the same atomic number .
(iii) The number of electrons present in the outermost shell of an atom is responsible for the formation of compounds either bysharing, accepting or donating electrons.
(iv) The chemical properti e s of an e l e m e nt ar e decided by its atomic numbers. Hence, atomic number is a more fundamental property of property of an element than its atomic mass.