Calculate the number of neutrons in the following. `""_19K^39`

Explanation

To calculate the number of neutrons in the potassium atom represented by `""_19K^39`, follow these steps:

### Step 1: Identify the Atomic Number and Mass Number
- The atomic number (Z) is represented by the subscript (19) in the notation `""_19K^39`. This indicates that the element is potassium (K) and has 19 protons.
- The mass number (A) is represented by the superscript (39). This is the total number of protons and neutrons in the nucleus of the atom.

### Step 2: Understand the Relationship Between Mass Number, Protons, and Neutrons
- The mass number (A) is the sum of the number of protons (Z) and the number of neutrons (N):
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