An atom of sodium has an atomic number of 11 and a mass number of 23. How many neutrons does it have?
A)11
B)12
C)23
D)34
E)35

Question

Quizplus · Accepted Answer

The atomic number of sodium is 11, which means it has 11 protons. 
The mass number is 23, which is equal to the sum of protons and neutrons. 
Mass number = protons + neutrons 
23 = 11 + neutrons 
Neutrons = 23 - 11 = 12 
Therefore, the sodium atom has 12 neutrons.

An Atom of Sodium Has an Atomic Number of 11