Atomic Theory and Structure Concepts

What did Democritus propose about the composition of matter?

• Matter is made of four elements: Earth, Wind, Water, and Fire.

• Matter is composed of tiny, indivisible particles called "atomos" surrounded by empty space.

• Atoms are uniformly packed spheres of positive matter filled with negatively charged electrons.

• Electrons orbit the nucleus at fixed energies and distances.

What was a key aspect of John Dalton's atomic theory?

• He proposed that matter is made of four fundamental elements.

• He demonstrated that common substances always broke down into the same elements in the same proportions, suggesting compounds are combinations of atoms.

• He discovered that atoms contain negatively charged electrons.

• He concluded that electrons orbit the nucleus in fixed energy levels.

Which scientist discovered the electron and proposed the "chocolate chip cookie" model of the atom?

• Democritus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

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What did Ernest Rutherford's gold foil experiment reveal about the atom?

• Atoms are uniformly packed spheres of positive matter.

• Electrons orbit the nucleus in fixed energy levels.

• Atoms consist largely of empty space with a dense, positively charged nucleus.

• Electrons behave simultaneously as both particles and waves.