Nucleon

The CED defines the word in a parenthesis. Essential knowledge 15.7.A.1 reads that the strong force is exerted at nuclear scales and dominates the interactions of nucleons "(protons or neutrons)". Statement 15.8.A.2.i glosses the count the same way, calling nucleon number "the number of neutrons and protons".

Two labels for one number. Nucleon number and mass number are the same quantity, written $A$, and it sits above the element symbol in nuclear notation. With $Z$ protons below it, the neutron count is $A - Z$, which is the step a question about neutrons wants and a question about nucleons does not.

Conservation of nucleon number is the rule that makes nuclear equations solvable. Statement 15.7.A.2 says possible nuclear reactions are constrained by it, and 15.8.A.2.i repeats it for decays. Alpha decay moves four nucleons out as a unit, beta decay converts one nucleon into the other type without changing the total, and gamma decay moves none. Add the top row on both sides of an equation and the totals must match.

Mass number is a count, not a mass. It has no units. The sheet prints both nucleon masses as $1.67 \times 10^{-27}$ kg, so $A$ times that figure is a rough mass for the nuclide, and only a rough one: a bound nucleus weighs less than its separated parts, which is what binding energy measures.