How many neutrons are in a typical silicon atom?

A. 15

B. 14

C. 28

D. 42

Silicon (Si) atomic mass is 28.085.

To find the mass number of most common isotope we need to round atomic mas to wholes.

28.085≈28 is atomic mass

Atomic number (number of protons) is an ordinal number of an element in the Periodic Table.

For silicons it is 14.

Mass number=number of protons (atomic number) + number of neutrons.

Number of neutrons=Mass number - Number of Protons (atomic number)

Number of neutrons = 28 - 14 = 14

Correct answer is B. 14