4.5.111 - Nucleon number and proton number

Understand what is meant by nucleon number (mass number) and proton number (atomic number).

Use - nucleon number and proton number to connect the rule to the data and decision in the question.

This matters because - nucleon number and proton number determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - nucleon number and proton number to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Nucleon number and proton number is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.