Answer: 48 neutrons
Step-by-step explanation:
Mass number is defined as the sum of number of protons and neutrons that are present in an atom.
Mass number = Number of protons + Number of neutrons
Atomic number is defined as the number of protons or number of electrons that are present in an atom.
Atomic number = Number of electrons = Number of protons
Given: Atomic number of Krypton = Number of electrons = Number of protons = 36
Mass number of krypton = Number of protons + Number of neutrons = 84
Thus, 84= 36 + Number of neutrons
Number of neutrons = 48
Thus krypton has 48 neutrons.