Question

25
how many neutrons does potassium - 42 have? (1 point)
42
19
23
39

Explanation:

Step1: Recall the formula for calculating neutrons

The formula is \( \text{Number of neutrons}=\text{Mass number}-\text{Atomic number}\).

Step2: Identify the mass number and atomic number

For Potassium - 42, the mass number \(A = 42\). The atomic number of potassium \(Z=19\) (from the periodic table).

Step3: Calculate the number of neutrons

Substitute the values into the formula: \(N=A - Z\). So \(N = 42-19\).

$$N=23$$

Answer:

C. 23