How many protons z and how many neutrons n are there in a nucleus of the most common isotope of silicon, 2814si?

The 28 is the sum of the protons and neutrons in the element silicon.

ALL silicon atoms have 14 protons in the nucleus, so we can turn this into an equation:

#protons + #neutrons = 28

14 + #neutrons = 28

#neutrons = 14

#protons = 14