Particle Physics: Question 1

Worked solution

Step 1: Find the nucleon number

The nucleon number $A$ is the total number of protons and neutrons in the nucleus: $A = 18 + 22 = 40$

Step 2: Identify the proton number

The proton (atomic) number $Z$ is simply the number of protons: $Z = 18$

Step 3: Apply the nuclide notation convention

Nuclide notation is written as $^{A}_{Z}\text{X}$, with the nucleon number $A$ as a superscript and the proton number $Z$ as a subscript, both to the left of the element symbol. Substituting the values found above: $^{40}_{18}\text{X}$

This is option B.

Step 4: Why the other options are wrong

• Option A, $^{18}_{22}\text{X}$, puts the proton number (18) on top and the neutron number (22) on the bottom. Neither position correctly holds the nucleon number or the proton number.
• Option C, $^{22}_{18}\text{X}$, puts the neutron number (22) on top instead of the nucleon number (40), even though the proton number on the bottom (18) is correct.
• Option D, $^{40}_{22}\text{X}$, correctly finds the nucleon number (40) for the top, but puts the neutron number (22) on the bottom instead of the proton number (18).

Final answer

• The correct nuclide notation is $\boxed{^{40}_{18}\text{X}}$, option B.