Plum pudding model

The plum pudding model pictured an atom as electrons embedded in a diffuse sphere of positive charge. J. J. Thomson proposed it before experiments revealed the nucleus.

J. J. Thomson: English physicist who discovered the electron and proposed an early model of atomic structure. He proposed the model, placing negatively charged electrons within distributed positive charge.
Cathode ray: A stream of electrons produced in a vacuum tube and accelerated by an electric field. Cathode-ray studies led Thomson to identify electrons before proposing the model.
Dalton's atomic theory: The theory that matter consists of atoms, which combine in fixed proportions in chemical compounds. It describes atoms without internal parts, unlike Thomson’s electron-containing model.
Electron discovery: The identification of the electron as a particle smaller than the atom, established by J. J. Thomson’s experiments. The model incorporated the newly recognized electron into an account of the whole atom.
Electron: A stable subatomic particle with negative electric charge, found in atoms and many other systems. The model’s electrons supplied negative charge within the positively charged sphere.
Cathode-ray tube: A vacuum tube in which an electron beam produces a visible spot on a phosphor-coated screen. Experiments with these tubes provided evidence that atoms contain negatively charged particles.
Bohr model: An atomic model in which electrons occupy specific allowed orbits around a nucleus. It retained a nucleus while adding quantized electron orbits absent from Thomson’s picture.
Atomic theory: A body of scientific ideas describing the composition and behavior of matter in terms of atoms. This model was an influential stage in the changing scientific account of atomic structure.
Electric charge: A physical property that determines electromagnetic interactions between particles and objects. Opposing charges balance in the model, making the atom electrically neutral.
Rutherford scattering experiment: An experiment in which alpha particles were directed at thin metal foil to investigate atomic structure. The large-angle deflections contradicted the diffuse charge distribution predicted by this model.

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