Answer : The correct option is, (b) atomic number
Explanation:
As we know that an atom is the smallest unit of a matter that consist of three subatomic particles which are electrons, protons and neutrons.
The protons and the neutrons are located inside the nucleus or center of the nucleus where the mass of the an atom is concentrated and the electrons are located around the nucleus.
The protons are positively charged, the electrons are negatively charged and the neutrons are neutral that means it has no charge.
Atomic number : It is equal to number of protons in the nucleus of an atom.
Atomic number = number of protons
Mass number : It is defined as the sum of number of protons and number of neutrons.
Number of neutrons = Mass number - Number of protons
Hence, the correct option is, (b) atomic number
