Questions and Answers
Who was the first person to use the term atom?
Democritus
What theory describes Democritus's idea about dividing matter?
Theory of the Universe
What is the meaning of the term 'atomos'?
indivisible
There is an _____ space between atoms.
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Atoms are completely _____
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Who was the first scientist to adapt Democritus's theory into a modern atomic model?
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What does Dalton's Atomic Model state?
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Who discovered the electron?
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An electric charge is passed through the tube. It travels from _______ to _____.
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The charge is _________, so to see where it traveled a fluorescent screen is placed at the back of the tube.
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This beam will always travel ________ if not interfered with.
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The deflection coils each have a specific charge. One is ________ and the other is ________.
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What did Thomson show in relation to the charge and the negative coil?
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What theory explains what an atom should look like according to Thomson?
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What is another name known for the Thomson Atomic Model?
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Each atom is a ______ filled with positively charged 'fluid.'
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What are later called electrons in the context of Thomson's model?
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Who set up the famous Gold Foil Experiment?
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What did the Gold Foil Experiment demonstrate?
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What is the positive center of the foil called?
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Rutherford's Atomic Model is also called as ___________________________
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Who agreed with the planetary model but noted its flaws?
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What does the Rutherford-Bohr model state?
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What happens to an electron when it moves from one level to another?
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Electrons travel on a specific orbit or path.
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Who used Heisenberg's uncertainty principle to create a modern atomic model?
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Schrödinger's Atomic Model is also called _____________________
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What model explains that we can predict where an electron will probably be?
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Study Notes
Early Concepts of Atoms
- Democritus: A philosopher from 400 BC who coined the term "atom" and theorized that matter can be divided until reaching indivisible particles.
- Indivisible: The Greek word "atomos" implies that atoms cannot be divided further.
- Theory of the Universe: Democritus proposed that all matter consists of these indivisible atoms separated by empty space.
Development of Atomic Theory
- John Dalton: In the 1800s, he developed the first modern atomic model based on Democritus's ideas, highlighting that all matter consists of atoms and defining elements by atomic weight.
- Dalton’s Atomic Model: Key ideas include atoms being indestructible, atoms of the same element being identical, and atoms combining to form compounds during reactions.
Discovery of Electrons
- J.J. Thomson: A scientist from the 1890s credited with discovering the electron through experiments with cathode ray tubes.
- Cathode Ray Experiment: An electric charge travels from cathode to anode, making the charge invisible and requiring a fluorescent screen to detect its path.
- Thomson's Atomic Model: Often called the "Plum Pudding Model," suggesting that atoms consist of positively charged 'fluid' with negatively charged electrons embedded within.
Revelation of Atomic Structure
- Ernest Rutherford: Known for the Gold Foil Experiment in the 1910s, he challenged Thomson's model, discovering a dense positive center (nucleus) in the atom due to nuclear deflections of alpha particles.
- Gold Foil Experiment: Most alpha particles passed through gold foil, but some were deflected, indicating a small, dense, positively charged nucleus.
Advancements in Atomic Models
- Planetary Model: Rutherford’s model, likened to a solar system with electrons orbiting the nucleus.
- Niels Bohr: In the 1910s, he refined the planetary model, introducing quantized orbits for electrons, where lower energy electrons occupy lower orbits.
Modern Atomic Theory
- Rutherford-Bohr Model: Describes electron orbits with set sizes and energies; electrons fill lower energy levels before higher ones.
- Radiation: Occurs when an electron transitions between different energy levels.
- Limitations: Electrons do not travel in fixed orbits, challenging the previous models.
Quantum Mechanics
- Erwin Schrödinger: A 1920s physicist who developed a more advanced atomic model using Heisenberg's uncertainty principle.
- Cloud Model: Also known as Schrödinger's model, it depicts electrons in probabilistic distributions rather than defined paths, predicting where they might be rather than exact locations.
Key Terms and Concepts
- Nucleus: The positively charged center of the atom that contains protons.
- Corpuscles: The term later used for electrons, which are negatively charged particles.
- Cloud Model: Highlights the probability of an electron's location based on energy levels, diverging from fixed orbits.
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Description
Explore the foundational ideas of atomic theory through key figures like Democritus. This quiz includes important definitions and concepts that have shaped our understanding of atoms. Test your knowledge on the historical timeline of atomic science.
