Final answer:
The atomic number (Z) of an element represents the number of protons in the nucleus and provides information about the number of electrons. The number of neutrons can be calculated by subtracting the atomic number from the mass number (A).
Step-by-step explanation:
The atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element. It determines the identity of the atom. The atomic number also indicates the number of electrons in an atom, as a neutral atom has the same number of protons and electrons. The number of neutrons can be calculated by subtracting the atomic number from the mass number (A).