Question

atoms of the element potassium have 19 protons. one of the most stable types of potassium atoms has the mass number 39. how many neutrons make up one of these potassium atoms? 19 20 38 58

Explanation:

Step1: Recall the formula for mass number

Mass number \(A=\) number of protons \(p+\) number of neutrons \(n\).

Step2: Substitute the known values

Given \(A = 39\) (mass number) and \(p=19\) (number of protons). Then \(n=A - p\).

$$n=39 - 19$$

$$n = 20$$

Answer:

20