Rutherford model | Definition, Description, Image, & Facts (2024)

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What is the model of the atom proposed by Ernest Rutherford?

The atom, as described by Ernest Rutherford, has a tiny, massive core called the nucleus. The nucleus has a positive charge. Electrons are particles with a negative charge. Electrons orbit the nucleus. The empty space between the nucleus and the electrons takes up most of the volume of the atom.

atomLearn about the smallest unit of matter, the atom.

Ernest RutherfordRead more about Ernest Rutherford, the physicist whose gold-foil experiment revealed key information about the structure of atoms.

What is the Rutherford gold-foil experiment?

A piece of gold foil was hit with alpha particles, which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space. Some particles had their paths bent at large angles. A few even bounced backward. The only way this would happen was if the atom had a small, heavy region of positive charge inside it.

alpha particleLearn about the particles used in the Rutherford gold-foil experiment.

What were the results of Rutherford's experiment?

The previous model of the atom, the Thomson atomic model, or the “plum pudding” model, in which negatively charged electrons were like the plums in the atom’s positively charged pudding, was disproved. The Rutherford atomic model relied on classical physics. The Bohr atomic model, relying on quantum mechanics, built upon the Rutherford model to explain the orbits of electrons.

Thomson atomic modelRead about the Thomson atomic model—the earliest model of atomic structure—and how Ernest Rutherford’s gold-foil experiment disproved it.

Bohr modelLearn about Niels Bohr’s atomic model and how it differs from Ernest Rutherford’s atomic model.

What did Ernest Rutherford's atomic model get right and wrong?

The Rutherford atomic model was correct in that the atom is mostly empty space. Most of the mass is in thenucleus, and the nucleus is positively charged. Far from the nucleus are the negatively charged electrons. But the Rutherford atomic model used classical physics and not quantum mechanics. This meant that an electron circling the nucleus would give off electromagnetic radiation. The electron would lose energy and fall into the nucleus. In the Bohr model, which used quantum theory, the electrons exist only in specific orbits and canmove between these orbits.

electromagnetic radiationLearn more about electromagnetic radiation and why it posed a problem for Ernest Rutherford’s atomic model.

quantumRead about the theory used in the Bohr model to more correctly describe the structure of atoms.

What was the impact of Ernest Rutherford's theory?

The gold-foil experiment showed that the atom consists of a small, massive, positively charged nucleus with the negatively charged electrons being at a great distance from the centre. Niels Bohr built upon Rutherford’s model to make his own. In Bohr’s model the orbits of the electrons were explained by quantum mechanics.

Niels BohrRead more about Danish physicist Niels Bohr, the first physicist to apply quantum theory to the problem of atomic structure.

Rutherford model, description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford. The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun.

The nucleus was postulated as small and dense to account for the scattering of alpha particles from thin gold foil, as observed in a series of experiments performed by undergraduate Ernest Marsden under the direction of Rutherford and German physicist Hans Geiger in 1909. A radioactive source emitting alpha particles (i.e., positively charged particles, identical to the helium atom nucleus and 7,000 times more massive than electrons) was enclosed within a protective lead shield. The radiation was focused into a narrow beam after passing through a slit in a lead screen. A thin section of gold foil was placed in front of the slit, and a screen coated with zinc sulfide to render it fluorescent served as a counter to detect alpha particles. As each alpha particle struck the fluorescent screen, it produced a burst of light called a scintillation, which was visible through a viewing microscope attached to the back of the screen. The screen itself was movable, allowing Rutherford and his associates to determine whether or not any alpha particles were being deflected by the gold foil.

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Most alpha particles passed straight through the gold foil, which implied that atoms are mostly composed of open space. Some alpha particles were deflected slightly, suggesting interactions with other positively charged particles within the atom. Still other alpha particles were scattered at large angles, while a very few even bounced back toward the source. (Rutherford famously said later, “It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.”) Only a positively charged and relatively heavy target particle, such as the proposed nucleus, could account for such strong repulsion. The negative electrons that balanced electrically the positive nuclear charge were regarded as traveling in circular orbits about the nucleus. The electrostatic force of attraction between electrons and nucleus was likened to the gravitational force of attraction between the revolving planets and the Sun. Most of this planetary atom was open space and offered no resistance to the passage of the alpha particles.

The Rutherford model supplanted the “plum-pudding” atomic model of English physicist Sir J.J. Thomson, in which the electrons were embedded in a positively charged atom like plums in a pudding. Based wholly on classical physics, the Rutherford model itself was superseded in a few years by the Bohr atomic model, which incorporated some early quantum theory. See also atomic model.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Melissa Petruzzello.