All 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 ss

## Step 1<br />The number of protons in an atom is referred to as the atomic number. For potassium, the atomic number is 19, which means all potassium atoms have 19 protons.<br /><br />## Step 2<br />The mass number of an atom is the sum of the number of protons and neutrons in its nucleus. Given that the mass number of this potassium atom is 39, we can determine the number of neutrons by subtracting the number of protons from the mass number.<br /><br />### **Number of neutrons = Mass number - Number of protons**<br /><br />## Step 3<br />Substitute the given values into the formula:<br /><br />### **Number of neutrons = 39 - 19 = 20**<br /><br />Therefore, one of these potassium atoms has 20 neutrons.