Concept:The atomic number of an atom is defined by the number of protons present in its nucleus.
Explanation:It is denoted by the symbol
Z.
The atomic number is unique for each element and determines the element's identity.
In a neutral atom, the number of electrons equals the number of protons, so atomic number also equals the electron count in a neutral atom.
The total number of protons and neutrons together is called the mass number, not the atomic number.
Therefore, the correct definition is the total number of protons present in the nucleus.
Answer:Option A: total number of protons present in the nucleus of an atom.