The atomic number of an element is determined by the number of protons in the nucleus of an atom. Since the atomic number (denoted as \( Z \)) uniquely identifies an element, it tells us how many protons are present.
The mass number of an atom is calculated by adding the number of protons and neutrons in the nucleus. The mass number (denoted as \( A \)) is given by the formula:
\[ A = Z + N \]
where \( Z \) is the number of protons and \( N \) is the number of neutrons. Thus, both protons and neutrons are used to calculate the mass number. Electrons are not included in the mass number calculation because their mass is negligible compared to that of protons and neutrons.
3 answers