Question

Which of the following describes an isotope containing 18 protons and 20 neutrons?

A. Calcium-38
B. Argon-40
C. Argon-38
D. Argon-20

Answer 1

It’s c

The reason why is because argon has 18 protons because that’s it atomic number. Now to determine the mass number we need the number of protons and neutrons added together. The prompt said 20 neutrons so we would add 20 to 18 which is equal to 38. Making c the right answer