The correct answer is C. Proton and Neutron.
The nucleus of an atom is made up of protons and neutrons, which are collectively called nucleons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. The number of protons in the nucleus is called the atomic number, and it determines the chemical element of the atom. For example, all atoms with 6 protons in their nucleus are carbon atoms. The number
of neutrons in the nucleus is called the neutron number, and it can vary for atoms of the same element. Atoms with the same number of protons but different numbers of neutrons are called isotopes.The protons and neutrons in the nucleus are held together by the strong force, which is a very powerful force that acts over very short distances. The electrons are held around the nucleus by the electric force, which is a force that acts between charged particles. The electrons are not part of the nucleus, but they are still considered to be part of the atom.
The nucleus is very small compared to the atom as a whole. The radius of the nucleus is typically about 10^-15 meters, while the radius of the atom is typically about 10^-10 meters. This means that the nucleus is about 100,000 times smaller than the atom.
The nucleus is also very dense. The density of the nucleus is typically about 10^17 kilograms per cubic meter, which is about 100 million times
the density of lead. This high density is due to the fact that the protons and neutrons in the nucleus are packed very closely together.The nucleus is a very important part of the atom. It contains most of the mass of the atom, and it determines the chemical properties of the atom.