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Questions and Answers
According to Dalton’s Atomic Theory, what is the postulate about the indivisibility of an atom?
Which statement best describes one of the drawbacks of Dalton’s Atomic Theory?
In Modern Atomic Theory, what postulate differs from Dalton’s theory regarding the structure of atoms?
What aspect of Rutherford's Atomic Model was different from Dalton’s Atomic Theory?
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Which characteristic of atoms did Planetary Model aim to explain?
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How does Modern Atomic Theory differ from Dalton’s Atomic Theory regarding isotopes?
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What did the discovery about the indivisibility of an atom challenge in Dalton’s theory?
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According to Modern Atomic Theory, what is a key characteristic of all atoms of the same element?
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What was proven wrong about atoms combining in simple whole-number ratios according to Modern Atomic Theory?
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Study Notes
Atomic Models
- Rutherford's atomic model resembles the planetary motion in the solar system, also known as the Planetary Model.
- Niels Bohr's atomic model overcame the limitations of Rutherford's model based on the Quantum Theory.
- The Bohr Model consists of five principles:
- Electrons are arranged in concentric circular orbits around the nucleus.
- Electrons occupy only certain stable orbits or shells.
- Each orbit or shell is associated with a definite fixed amount of energy, also called energy levels.
- Energy levels increase with distance from the nucleus.
- Electrons do not lose energy while revolving in a particular orbit.
Discovery of the Neutron
- In 1932, French physicists Frederic and Irene Joliot-Curie bombarded beryllium nuclei with α-particles, releasing unknown radiation.
- The Joliot-Curies initially hypothesized that the radiation was γ-rays.
Historical Development of Atomic Theories
- Ancient Greek philosopher Empedocles believed that all materials are made up of four elements: earth, air, water, and fire.
- Plato adopted Empedocles' theory and coined the term "element" to describe these four substances.
- Aristotle adopted Empedocles' theory and introduced the idea of differentiating elements based on properties.
- Democritus taught the theory of atomism, believing that indivisible and indestructible atoms are the basic components of all matter.
The Greek Concept of 'Atomos'
- Around 440 BC, Leucippus originated the atom concept, which was refined and extended by Democritus.
- The Greek concept of 'atomos' consists of five major points:
- All matter is composed of atoms, which are bits of matter too small to be seen.
- There is a void, which is an empty space between atoms.
- Atoms are completely solid.
- Atoms are homogeneous, with no internal structure.
- Atomic Theory is the way to interpret facts about atoms.
Dalton's Atomic Theory
- Dalton studied the weights of various elements and compounds.
- Postulates of Dalton's Atomic Theory:
- Elements are made of small particles called atoms.
- Atoms can neither be created nor destroyed.
- All atoms of the same element are identical and have the same mass and size.
- Atoms of different elements have different masses and size.
- Atoms combine in small whole numbers to form compounds.
Modern Atomic Theory
- Drawbacks of Dalton's Atomic Theory:
- The indivisibility of an atom was proved wrong.
- Atoms of the same element are similar in all properties was proved wrong.
- Atoms of different elements differ in mass was proved wrong.
- Atoms of different elements combine in simple whole-number ratios to form compounds was proved wrong.
- Modern Atomic Theory Postulates:
- Elements are made of small particles called atoms.
- Atoms cannot be created or destroyed during ordinary chemical reactions.
- All atoms of the same element have the same atomic number but may vary in mass number due to the presence of different isotopes.
- Atoms of different elements are different.
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Description
This quiz covers the characteristics and principles of Rutherford's Planetary Model and Niels Bohr's Atomic Model. Learn about the arrangement of electrons, the structure of the atom, and the differences between the two models.
