Which of the following defines the atomic number of an atom

Answer 1

The atomic number of an atom is defined as the number of protons present in the nucleus of that atom. It is unique to each element and determines the chemical properties and identity of the element. For example, hydrogen has an atomic number of 1 (one proton), helium has an atomic number of 2 (two protons), and so forth. The atomic number also defines the element in the periodic table.