* Atomic Mass Number: The atomic mass number is the total number of protons and neutrons in an atom's nucleus.

* Given Information:

* You have 5 protons (since the atomic number defines the element, and the element is defined by its proton count).

* You have 6 neutrons.

* Calculation:

* Atomic Mass Number = Protons + Neutrons

* Atomic Mass Number = 5 + 6 = 11

Therefore, the atomic mass number of this atom is 11.