In the nucleus.
Nucleus
The nucleus, made up of protons and neutrons, contains most of an atom's mass.
There are two main parts of an atom. The one that contains the most mass is the nucleus, which holds all of the protons and neutrons in a ball at the center of the atom. The second part is the cloud of electrons that orbit the nucleus. So, protons are found in the nucleus of an atom.
The most mass of a atom is located in the nucleus, where the protons and the neutrons are located.
The nucleus contains the mass.
The vast majority of an atom's mass is within the nucleus; the electrons orbiting the nucleus, which do contain the same amount of charge as the nucleus(albeit negative), have virtually no mass when compared to the nucleus. In fact many scientific disciplines disregard the mass of electrons altogether.
The smallest part of an atom would be a quark. Quarks are either up or down quarks, and have virtually no mass. Neutrinos have even less mass, but are not part of an atom.
the nucleus of the atom
the nucleus
It is the part of the atom with the greatest mass
The protons and neutrons found in the nucleus are responsible for the majority of the atom mass while the much smaller electrons orbit the nucleus.
The electron.