It is not correct to say that electrons do not have any mass. Electrons do have mass, although it is significantly smaller compared to the mass of protons and neutrons. The mass of an electron is approximately 9.109 × 10^-31 kilograms or 0.00054858 atomic mass units (u).
In an atom, the mass is primarily concentrated in the nucleus, which contains protons and neutrons. Protons have a positive charge and a mass of approximately 1.0073 atomic mass units, while neutrons have no charge and a mass of approximately 1.0087 atomic mass units. These values are much larger than the mass of electrons.
The overall mass of an atom is determined by the combined mass of its protons, neutrons, and electrons. Although electrons have a much smaller mass compared to protons and neutrons, their presence still contributes to the total mass of an atom. However, in most cases, when calculating the atomic mass of an element, the mass of electrons is negligible compared to the mass of protons and neutrons, so it is often not included.
It is important to note that the mass of an electron is part of the total mass of an atom, and it plays a crucial role in determining the chemical and physical properties of elements. The interaction between electrons and the nucleus, as well as the distribution of electrons in atomic orbitals, governs the behavior and reactivity of atoms.