The sizes of electrons and protons, as well as atoms, can be described in different ways. Here are a few perspectives:
Relative Size: If we consider the size of an atom as a whole, electrons are much smaller compared to the entire atom. The size of an atom is typically on the order of angstroms (Å), with an angstrom being equal to 0.1 nanometers (nm). In comparison, the size of an electron is estimated to be around 10^-15 meters (1 femtometer or fm), which is about 10,000 times smaller than the size of an atom. Protons, on the other hand, have a size similar to or slightly larger than neutrons and are also on the order of femtometers.
Electron Cloud: Electrons do not have a well-defined size or position like solid particles. Instead, they are described by a probability distribution known as the electron cloud or orbital. The electron cloud represents the region where the electron is most likely to be found. The shape and extent of the electron cloud determine the size of the atom. The size of an atom is usually defined by its outermost electron shell or the average distance of the outermost electrons from the nucleus.
Nucleus: The nucleus of an atom contains protons and neutrons tightly packed together. Protons and neutrons have a size on the order of femtometers, but they are much smaller compared to the overall size of the atom. The nucleus occupies only a tiny fraction of the total atomic volume.
In summary, electrons are significantly smaller than atoms, with a size estimated to be around 10^-15 meters. Protons and neutrons are similar in size to electrons but are still much smaller than the overall size of an atom. The size of an atom is primarily determined by the distribution of electrons in their electron clouds.