Podcast
Questions and Answers
What is the Law of Conservation of Mass, as proposed by John Dalton?
What is the Law of Conservation of Mass, as proposed by John Dalton?
What is the purpose of the low pressure in a discharge tube?
What is the purpose of the low pressure in a discharge tube?
What is the name of the experiment conducted by William Crookes to demonstrate the existence of cathode rays?
What is the name of the experiment conducted by William Crookes to demonstrate the existence of cathode rays?
What is the charge of cathode rays, as concluded by J.J. Thomson?
What is the charge of cathode rays, as concluded by J.J. Thomson?
Signup and view all the answers
What is the significance of the shadow observed in the glowing area of the glass tube in the Maltese Cross Experiment?
What is the significance of the shadow observed in the glowing area of the glass tube in the Maltese Cross Experiment?
Signup and view all the answers
What is the conclusion made by J.J. Thomson regarding the existence of sub-atomic particles?
What is the conclusion made by J.J. Thomson regarding the existence of sub-atomic particles?
Signup and view all the answers
What is the composition of an atom, according to the modern understanding?
What is the composition of an atom, according to the modern understanding?
Signup and view all the answers
What was the main component of JJ Thomson's Plum Pudding Model?
What was the main component of JJ Thomson's Plum Pudding Model?
Signup and view all the answers
Who suggested the name 'electron' for negatively charged particles?
Who suggested the name 'electron' for negatively charged particles?
Signup and view all the answers
What was the purpose of the oil drop experiment conducted by Robert Millikan?
What was the purpose of the oil drop experiment conducted by Robert Millikan?
Signup and view all the answers
What was the conclusion drawn by Rutherford from the alpha-particle scattering experiment?
What was the conclusion drawn by Rutherford from the alpha-particle scattering experiment?
Signup and view all the answers
What was the name given to the neutral particles discovered by James Chadwick?
What was the name given to the neutral particles discovered by James Chadwick?
Signup and view all the answers
Who proposed a new model for the atom, suggesting that electrons were arranged in a series of concentric circular orbits?
Who proposed a new model for the atom, suggesting that electrons were arranged in a series of concentric circular orbits?
Signup and view all the answers
What was the outcome of the alpha-particle scattering experiment when an alpha-particle collided with the nucleus?
What was the outcome of the alpha-particle scattering experiment when an alpha-particle collided with the nucleus?
Signup and view all the answers
Who discovered that positively charged particles identical to a hydrogen atom were emitted when an atom was bombarded?
Who discovered that positively charged particles identical to a hydrogen atom were emitted when an atom was bombarded?
Signup and view all the answers
Study Notes
Atomic Theory
- All matter is composed of tiny particles called atoms.
- Atoms are indivisible, meaning they cannot be broken into simpler particles.
John Dalton's Contributions
- Proposed the atomic theory in 1808, including the Law of Conservation of Mass.
- Atoms cannot be created or destroyed in a chemical reaction.
Cathode Rays
- Scientists discovered that invisible particles traveled from the cathode (- terminal) to the anode (+ terminal) in a discharge tube.
- These particles were later found to be negatively charged.
William Crookes' Experiments
- Conducted experiments to demonstrate the existence of cathode rays.
- Performed the Maltese Cross experiment, showing that cathode rays travel in straight lines.
JJ Thomson's Contributions
- Conducted experiments into the charge and mass of cathode rays in 1897.
- Found that cathode rays were negatively charged and lighter than the lightest known atom.
- Proposed the Plum Pudding Model, where a positively charged pudding (proton) was balanced by negatively charged fruit (electrons).
Electron Discovery
- Johnstone Stoney suggested the name "electron" for these negatively charged particles.
- Robert Millikan measured the charge on an electron using the oil drop experiment in 1911.
Rutherford's Experiment
- Assumed that positive α-particles would be deflected as they passed through thin gold foil in 1911.
- Observed that:
- A large number of α-particles were not deflected at all.
- Many particles were deflected at small angles.
- A small number of particles were deflected at angles greater than 90°.
- A smaller number bounced back towards their source.
- Concluded that:
- The positive charge was concentrated into a dense nucleus in the centre of the atom.
- The rest of the atom was empty space, allowing α particles to travel through undisturbed.
Rutherford's Atomic Model
- Proposed a new model for the atom, where electrons are arranged in concentric circular orbits at increasing distances from the nucleus.
- These different orbits were called energy levels.
Protons and Neutrons
- Rutherford discovered that positively charged particles identical to a hydrogen atom were emitted when an atom was bombarded.
- Concluded that these positively charged particles were protons and made up the positive part of all atoms.
- James Chadwick produced evidence for the existence of neutral particles, called neutrons, in the nucleus.
Neil Bohr's Contributions
- Proposed an atomic model in 1913, building on Rutherford's work.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about the fundamental principles of atomic theory, including the indivisibility of atoms and the Law of Conservation of Mass. Discover how John Dalton's work laid the foundation for modern chemistry.
