Final answer:
The positively charged center of an atom consisting of protons and neutrons is called the nucleus, which is dense, has most of the atom's mass, and is orbited by negatively charged electrons.
Step-by-step explanation:
The positively charged center of the atom consisting of protons and neutrons is called the nucleus. The nucleus is at the center of an atom, composed of protons and neutrons and spanning approximately 10-15 meters. The protons carry a positive electric charge, while the neutrons are neutral. The atomic nucleus is incredibly dense and holds together the bulk of an atom's mass. Electrons, which have a negative electric charge, orbit the nucleus, filling the mostly empty space around it. The number of protons defines the element type—a hydrogen atom has one proton, while carbon has six, for instance.