Question

potassiums atomic number is 19, and its atomic mass is approximately 39. how many neutrons does potassium have? (1 point)
58
19
39
20

Explanation:

Step1: Recall the formula

Atomic mass = Protons + Neutrons, and atomic number = Protons.

Step2: Calculate neutrons

Neutrons = Atomic mass - Atomic number. Given atomic number = 19 and atomic mass = 39, so Neutrons = 39 - 19.

Step3: Get the result

39 - 19 = 20.

Answer:

D. 20