Question

If potassium's atomic mass is 39.10 amu and its atomic number is 19, how many neutrons does the most common isotope contain?
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21
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19
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39
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20

Answer 1

To find the number of neutrons in the most common isotope of potassium, you can use the formula:

\[
\text{Number of Neutrons} = \text{Atomic Mass} - \text{Atomic Number}
\]

Given that the atomic mass of potassium is approximately 39.10 amu and its atomic number is 19, the calculation would be:

\[
\text{Number of Neutrons} = 39.10 - 19 \approx 20.10
\]

Since we are looking for a whole number, we round to the nearest whole number, which is 20.

Therefore, the most common isotope of potassium contains **20 neutrons**.