In Rutherford's atomic model, what is at the center of the atom?

• A. A dense nucleus containing protons and neutrons
• B. The electron cloud surrounding the nucleus
• C. Electrons orbiting the nucleus
• D. A uniform positive sphere with embedded electrons

Answer: (C)

Rutherford's model places a tiny, dense nucleus at the center of the atom. This center contains positively charged protons, and in modern understanding also neutrons, making the nucleus much heavier than the rest of the atom. The rest of the atom is mostly empty space where electrons move around this nucleus, effectively orbiting it. So the thing at the center is the dense nucleus, not the electrons themselves or a spread-out positive sphere. The electron cloud describes where electrons are found around the nucleus, and the plum pudding idea (a uniform positive sphere with embedded electrons) is an older model that Rutherford’s experiment helped to disprove.