Early Atomic Theories and Models

Which scientist proposed the existence of atoms and the concept that they vary in size and mass?

Lucretius and Democritus conducted experiments to prove their theories about atoms.

What law did John Dalton discover that relates to how elements combine in chemical compounds?

J.J. Thomson is known for proposing the ________ model of the atom.

Match the following scientists with their contributions to atomic theory:

What did Lucretius and Democritus believe was necessary to explain changes in states of matter?

All atoms of a given element are identical according to Dalton's theory.

What term did J.J. Thomson use to refer to the negatively charged particles he discovered?

What model did Hanataro Nagaoka propose?

Ernest Rutherford's Gold Foil Experiment showed that atoms are mostly solid with little empty space.

Who combined Rutherford's nuclear model and Planck's quantum theory to create the Bohr model?

The __________ model uses mathematical equations to describe the likelihood of finding an electron in a certain position.

Match the physicists to their contributions:

What did Arnold Sommerfeld revise in the Bohr model?

Electrons in the Bohr model can remain in a specific orbit indefinitely.

What did the results of the Geiger-Marsden experiment demonstrate about the atom?

Atomic Theory Pioneers

Democritus and Lucretius proposed the existence of atoms, differing in size and mass, to explain changes in matter's states. They did not conduct experiments to support their theory.
John Dalton's Law of Multiple Proportions describes how elements combine in different ratios to form different compounds.
J.J. Thomson proposed the plum pudding model of the atom.

Scientists and Contributions

Democritus and Lucretius: Proposed the concept of atoms.
John Dalton: Developed Dalton's atomic theory, including the law of multiple proportions.
J.J. Thomson: Discovered the electron and proposed the plum pudding atomic model. He called negatively charged particles "corpuscles".
Hanataro Nagaoka: Proposed the Saturnian model of the atom.
Ernest Rutherford: Conducted the gold foil experiment, demonstrating that atoms are mostly empty space with a dense, positively charged nucleus.
Niels Bohr: Combined Rutherford's nuclear model and Planck's quantum theory to create the Bohr model.

Atomic Models and Revisions

The quantum mechanical model uses mathematical equations to describe electron probability distributions.
Arnold Sommerfeld revised the Bohr model by introducing elliptical orbits and energy sublevels.
Bohr's Model: Electrons exist within specific energy levels or orbits; can remain indefinitely in these orbits.
Geiger-Marsden experiment (Rutherford's Gold Foil Experiment): Demonstrated that the atom is mostly empty space with a small, dense, positively charged nucleus.

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