An atom's mass number is 13 and its atomic number is 6 How many neutrons are in its nucleus? 13 6 7 19

## Step 1<br />The mass number of an atom is the sum of the number of protons and neutrons in its nucleus. This is represented by the formula:<br />### **Mass Number = Number of Protons + Number of Neutrons**<br />## Step 2<br />The atomic number of an atom is the number of protons in its nucleus. This is represented by the formula:<br />### **Atomic Number = Number of Protons**<br />## Step 3<br />Given that the mass number is 13 and the atomic number is 6, we can find the number of neutrons by subtracting the atomic number from the mass number. This is represented by the formula:<br />### **Number of Neutrons = Mass Number - Atomic Number**<br />## Step 4<br />Substituting the given values into the formula, we get:<br />### **Number of Neutrons = 13 - 6 = 7**