How many neutrons are there in an atom of ${ } _ { 19 } ^ { 39 } \mathrm {~K}$ ?

Name: How many neutrons are there in an atom of ${ } _ { 19 } ^ { 39 } \mathrm {~K}$ ?
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Question

Quizplus · Accepted Answer

The number of neutrons in an atom can be calculated as follows:

Number of neutrons = Mass number - Atomic number

In this case, 
Mass number = 39 
Atomic number (number of protons) = 19

Therefore, 
Number of neutrons = 39 - 19 = 20

Hence, the correct answer is choice B.

How Many Neutrons Are There in an Atom Of 1939 K{ } _ { 19 } ^ { 39 } \mathrm {~K}1939​ K