An atom has 17 protons, 18 neutrons and 17 electrons. (a) Identify Z, N, A and the element. (b) What is its approximate mass in atomic mass units? (c) Write its nuclear symbol. Solution: (a) Z = 17 → chlorine (Cl). N = 18. A = Z + N = 35. (b) ≈ 35 u (each nucleon ≈ 1 u; electrons contribute negligibly, ~0.009 u total). (c) ³⁵₁₇Cl — mass number as superscript, atomic number as subscript. (This is chlorine-35, one of chlorine's two stable isotopes.)