Silicon (atomic number 14) has three isotopes: 28Si, 29Si, and 30Si.

What is the number of protons in an atom of silicon with the highest mass number?

14

16

29

30

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.