Question

Why is the atom of one element different from the atom of other emements?

Answer 1

atom of one element is different from the atom of other element as:-
1.They have different number of proton, neutron and electrons.
2.they have different physical and chemical properties.
HOPE THIS HELPS!

Answer 2

Normally, the number of electrons is equal to the number of protons, which makes the atoms electrically neutral. The number of protons in an atom is the defining feature of an atom. This is what makes an element different from another.
eg: HYDROGEN has 1 atom 
    : OXYGEN has 8 atoms