Question

jenny knows that the atomic number of the element potassium, k, is 19. she also knows that the average atomic mass can be used to find how many neutrons are in most atoms of an element. if the average atomic mass of potassium is 39.098, how many neutrons are found in most atoms of potassium? 19 20 39 40

Explanation:

Step1: Recall the relationship

The average atomic mass is approximately the sum of protons and neutrons. The atomic number is equal to the number of protons.

Step2: Identify number of protons

The atomic number of potassium is 19, so the number of protons is 19.

Step3: Calculate number of neutrons

Let the number of neutrons be $n$. We know that average atomic mass $\approx$ number of protons + number of neutrons. So $n\approx39.098 - 19$. Rounding the average atomic mass to 39, we get $n = 39 - 19=20$.

Answer:

B. 20