Question

How many neutrons are in a typical silicon atom?
A. 15
B. 14
C. 28
D. 42

Answer 1

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