Answer:
150 years
Step-by-step explanation:
The specific silicon isotope you are referring to has 14 protons and 18 neutrons. According to the Wikipedia page on isotopes of silicon, Silicon-32 is the silicon isotope with 14 protons and 18 neutrons. It is a radioactive isotope produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years.