Historical Development of Atomic Theory and Periodic Table

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Who proposed that matter could not be divided indefinitely and introduced the term 'atomos'?

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Democritus

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What did John Dalton propose in 1808?

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John Dalton proposed that atoms are tiny, indivisible particles and developed the first atomic theory and an early periodic table of 20 elements.

Front

Who discovered electrons and proposed the plum pudding model?

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J.J. Thomson

Front

What did Ernest Rutherford identify and demonstrate about atoms?

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Ernest Rutherford identified protons and the nucleus, demonstrating that atoms are mostly empty space.

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What was Niels Bohr's contribution to atomic theory?

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Niels Bohr proposed that electrons orbit the nucleus in specific shells.

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What concept did Erwin Schrödinger introduce?

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Erwin Schrödinger developed a mathematical model for electron locations, introducing the concept of electron clouds.

Front

Who discovered neutrons and what did this explain?

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James Chadwick discovered neutrons, explaining isotopes.

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What are isotopes?

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Isotopes are variants of the same element with the same number of protons but different numbers of neutrons, leading to different atomic masses.

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What did Johann Dobereiner contribute to the development of the periodic table?

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Johann Dobereiner grouped elements into triads based on similarities in 1829.

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What was John Newlands' contribution to the periodic table?

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John Newlands arranged elements by increasing mass number, identifying 'octaves' in 1864.