Answer: Option (2) is the correct answer.
Step-by-step explanation:
Atomic number of an atom means the total number of protons and atom contains. Each atom or element has different number of protons.
For example, atomic number of nitrogen is 7 whereas atomic number of sodium is 11.
This also means that in a nitrogen atom there are 7 protons and in a sodium atom there are 11 protons.
Thus, we can conclude that the property number of protons in the atomic nucleus is the best one to use for identification of an element.