An atom that has 14 protons and 17 neutrons is an isotope of which element?

This is an isotope of silicon since it has 14 protons.  for an element, you can have different numbers of neutrons, however, if you change the number of protons the identity of the element changes.

for example, carbon 14 and carbon 12 both have 6 protons.  The only thing that changed was the number of neutrons which went from 6 to 8.