Реши задание на изображении

Answer: the third option — Neutrons = mass number − atomic number.

Why it works

• Mass number \(A\) = protons + neutrons.
• Atomic number \(Z\) = number of protons.
• So, to leave only the neutrons, subtract the protons:

\[ \text{neutrons}=A-Z \]

Check with the sodium example in the image

\[ \text{neutrons}=23-11=12 \]

Sodium-23 has 11 protons and 12 neutrons, and \(11+12=23\). The first option would wrongly give 23 neutrons; the second treats the two numbers as equal, which they are not.