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Questions and Answers
What was the main limitation of Dalton's atomic model?
What was the main limitation of Dalton's atomic model?
- It regarded the atom as a solid sphere with no internal structure. (correct)
- It accurately described electron orbits.
- It suggested that electrons have a significant mass.
- It included protons but not neutrons.
Which observation was NOT part of the alpha scattering experiment results?
Which observation was NOT part of the alpha scattering experiment results?
- Most alpha particles passed straight through the foil.
- All alpha particles bounced back. (correct)
- Some alpha particles were deflected at large angles.
- Some alpha particles bounced back.
What was a significant conclusion of the nuclear model?
What was a significant conclusion of the nuclear model?
- Protons and neutrons are found outside the nucleus.
- Atoms do not have a defined mass.
- Electrons orbit the nucleus in fixed distances. (correct)
- Atoms consist solely of electrons and a positively charged cloud.
How does the relative mass of an electron compare to protons and neutrons?
How does the relative mass of an electron compare to protons and neutrons?
What discovery led to the understanding of neutrons in the nucleus?
What discovery led to the understanding of neutrons in the nucleus?
Flashcards
Dalton's Atomic Model
Dalton's Atomic Model
John Dalton's model of the Atom as a solid, indivisible sphere, without protons, neutrons, or electrons.
Plum Pudding Model
Plum Pudding Model
A model describing the atom as a positively charged sphere with negatively charged electrons embedded within it, like plums in pudding.
Alpha Scattering Experiment
Alpha Scattering Experiment
An experiment firing alpha particles at a thin gold foil, revealing the structure of the atom. Most particles pass straight through, some are deflected, and some bounce back.
Nuclear Model
Nuclear Model
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Electron Shell (Bohr) Model
Electron Shell (Bohr) Model
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Study Notes
Development of Atomic Models
- Dalton's model proposed the atom as an indivisible sphere.
- The plum pudding model suggested a positive cloud with negative electrons embedded.
- Rutherford's gold foil experiment led to the nuclear model, where a dense, positively charged nucleus contains protons, and electrons orbit around it.
- Later, Chadwick's experiments confirmed the existence of neutrons, which are neutral particles in the nucleus.
- Bohr's model refined the nuclear model, proposing electrons orbit the nucleus in specific energy levels (shells).
Alpha Particle Scattering
- Alpha particles (positively charged) were fired at a gold foil.
- Most particles passed straight through, indicating mostly empty space in atoms.
- Some particles were deflected, showing the presence of a concentrated positive charge (the nucleus).
- A few particles bounced back, demonstrating the extremely small size and high density of the nucleus.
Structure of the Atom
- Atoms consist of a nucleus containing protons (positive charge) and neutrons (neutral charge).
- Electrons (negative charge) orbit the nucleus.
- Protons and neutrons have a relative mass of 1.
- Electrons have a negligible relative mass (approximately 0).
- Electrons orbit the nucleus in shells / energy levels.
- The nucleus is very small compared to the overall size of the atom.
Relative Mass
- Protons and neutrons have a similar mass (1).
- Electrons have a much smaller mass (approximately 1/1800).
Atomic Size
- The radius of an atom is about 1 × 10⁻¹⁰ m.
- The radius of a nucleus is much smaller, approximately 1 × 10⁻¹⁴ m.
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