Question

What must differ between the atoms of two different elements

Answer 1

The number of protons and neutrons in the nucleolus of an atom.

Answer 2

Number of protons

Step-by-step explanation:

The atoms which belongs to different element must be different in the number of protons which leads to atomic number. This is also the basics of the classification of the elements on the basics of the increasing atomic number as each element has a unique number of protons. Hence, different number of protons leads to different elements.