Answer: 14
Explanation:
Isotopes are elements which have same atomic number but different mass number.
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
For silicon , as the atomic number is 14, the number of protons are also 14 for all the isotopes.
