Explanation:
The form AZX denoted that;
Z = The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of every atom of that element.
A = Mass Number ( Sum of Neutrons and Protons)
X represents the element.
A. the copper isotope with 34 neutrons
X = Cu
Atomic Number of Copper, Z = 29
Mass Number, A = 29 + 34 = 63
63.29.Cu
B. the copper isotope with 36 neutrons
X = Cu
Atomic Number of Copper, Z = 29
Mass Number, A = 29 + 36 = 65
65.29.Cu
C. the potassium isotope with 21 neutrons
X = K
Atomic Number of Potassium, Z = 19
Mass Number, A = 19 + 21 = 40
40.19.K
D. the argon isotope with 22 neutrons
X = Ar
Atomic Number of Argon, Z = 18
Mass Number, A = 18 + 22 = 40
40.18.Ar
