ATOMIC THEORY HISTORY

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Who proposed the first modern atomic theory?

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John Dalton proposed the first modern atomic theory in the early 19th century.

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What is the main idea of Dalton's atomic theory?

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Dalton's atomic theory states that all matter is made up of atoms, which are indivisible and indestructible.

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What did J.J. Thomson discover about the atom?

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J.J. Thomson discovered the electron and proposed the 'plum pudding' model of the atom, which suggests that atoms contain negatively charged electrons embedded in a positively charged 'soup'.

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What is the significance of Rutherford's gold foil experiment?

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Rutherford's gold foil experiment demonstrated that atoms have a small, dense nucleus that contains most of the atom's mass, leading to the nuclear model of the atom.

Front

What does the Bohr model of the atom propose?

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The Bohr model proposes that electrons travel in fixed orbits around the nucleus and that these orbits correspond to specific energy levels.

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Define 'atomic number'.

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The atomic number is the number of protons in the nucleus of an atom, which determines the element's identity.

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Define 'mass number'.

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The mass number is the total number of protons and neutrons in an atom's nucleus.

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How do you calculate the number of neutrons in an atom?

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To calculate the number of neutrons, subtract the atomic number from the mass number: Neutrons = Mass Number - Atomic Number.

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What is the 'plum pudding' model?

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The 'plum pudding' model is a theory proposed by J.J. Thomson that describes the atom as a sphere of positive charge with negatively charged electrons scattered throughout.

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What did Democritus contribute to atomic theory?

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Democritus was the first to propose that matter is made up of small, indivisible particles called 'atomos'.