Podcast
Questions and Answers
What gives rise to the existence of positive rays in an atom?
What gives rise to the existence of positive rays in an atom?
Which statement accurately describes the properties of anode rays?
Which statement accurately describes the properties of anode rays?
What was the main conclusion of Eugen Goldstein's experiments?
What was the main conclusion of Eugen Goldstein's experiments?
What is the primary difference between anode rays and cathode rays?
What is the primary difference between anode rays and cathode rays?
Signup and view all the answers
According to Thomson's atomic model, how is the atom described?
According to Thomson's atomic model, how is the atom described?
Signup and view all the answers
What do cathode rays consist of?
What do cathode rays consist of?
Signup and view all the answers
What behavior do cathode rays exhibit in the presence of an electric field?
What behavior do cathode rays exhibit in the presence of an electric field?
Signup and view all the answers
What is the charge-to-mass ratio of a cathode ray particle measured by J.J. Thomson?
What is the charge-to-mass ratio of a cathode ray particle measured by J.J. Thomson?
Signup and view all the answers
What value did Millikan find for the basic charge of the electron?
What value did Millikan find for the basic charge of the electron?
Signup and view all the answers
What can be concluded about the path of cathode rays?
What can be concluded about the path of cathode rays?
Signup and view all the answers
What is the equation used to describe the electric field in the Millikan Oil Drop Experiment?
What is the equation used to describe the electric field in the Millikan Oil Drop Experiment?
Signup and view all the answers
Which of the following statements is true about cathode rays and their interaction with materials?
Which of the following statements is true about cathode rays and their interaction with materials?
Signup and view all the answers
Which experiment is associated with measuring the basic charge of the electron?
Which experiment is associated with measuring the basic charge of the electron?
Signup and view all the answers
What is the average atomic mass of chlorine based on its isotopes and their abundances?
What is the average atomic mass of chlorine based on its isotopes and their abundances?
Signup and view all the answers
How is one atomic mass unit (amu) defined?
How is one atomic mass unit (amu) defined?
Signup and view all the answers
What contribution does the isotope 12C have to the average atomic mass of carbon?
What contribution does the isotope 12C have to the average atomic mass of carbon?
Signup and view all the answers
If an element has three isotopes, how would you calculate the average atomic mass?
If an element has three isotopes, how would you calculate the average atomic mass?
Signup and view all the answers
What is the percentage abundance of the isotope 13C in natural carbon?
What is the percentage abundance of the isotope 13C in natural carbon?
Signup and view all the answers
What did Chadwick conclude about the invisible radiations emitted from the Beryllium nucleus?
What did Chadwick conclude about the invisible radiations emitted from the Beryllium nucleus?
Signup and view all the answers
How are isotopes of an element defined?
How are isotopes of an element defined?
Signup and view all the answers
What observation did Chadwick make regarding the paddle wheel during the experiment?
What observation did Chadwick make regarding the paddle wheel during the experiment?
Signup and view all the answers
Which of the following describes the atomic weight of an element?
Which of the following describes the atomic weight of an element?
Signup and view all the answers
In Chadwick's experiments, what happened when the radiations passed through an electric field?
In Chadwick's experiments, what happened when the radiations passed through an electric field?
Signup and view all the answers
If a helium nucleus only contained protons, what would be its mass relative to hydrogen?
If a helium nucleus only contained protons, what would be its mass relative to hydrogen?
Signup and view all the answers
What did earlier scientists believe the radiations emitted from Beryllium were?
What did earlier scientists believe the radiations emitted from Beryllium were?
Signup and view all the answers
Which of the following statements about neutrons is true?
Which of the following statements about neutrons is true?
Signup and view all the answers
What does Rutherford's conclusion suggest about the majority of the atom's structure?
What does Rutherford's conclusion suggest about the majority of the atom's structure?
Signup and view all the answers
According to Rutherford's model, which part of the atom is responsible for its positive charge?
According to Rutherford's model, which part of the atom is responsible for its positive charge?
Signup and view all the answers
What was a significant drawback of Rutherford's atomic model?
What was a significant drawback of Rutherford's atomic model?
Signup and view all the answers
In Rutherford's planetary model of the atom, what do the electrons represent?
In Rutherford's planetary model of the atom, what do the electrons represent?
Signup and view all the answers
What observation led Rutherford to conclude that there are small, dense regions within the atom?
What observation led Rutherford to conclude that there are small, dense regions within the atom?
Signup and view all the answers
What explains the electrical neutrality of an atom according to Rutherford's conclusions?
What explains the electrical neutrality of an atom according to Rutherford's conclusions?
Signup and view all the answers
Which of the following was NOT a conclusion drawn by Rutherford from his scattering experiment?
Which of the following was NOT a conclusion drawn by Rutherford from his scattering experiment?
Signup and view all the answers
What was one of the limitations of the experimental method used by Rutherford?
What was one of the limitations of the experimental method used by Rutherford?
Signup and view all the answers
Study Notes
Cathode Ray Experiment
- Invisible rays emitted from the cathode
- The rays cause a green fluorescent glow on hitting the tube wall
- The rays act like negatively charged particles in an electric field
- The rays travel in straight lines and are independent of the cathode material
Properties of Cathode Ray Particles
- Negatively charged
Cathode Ray: Charge/Mass Ratio (e/m)
- J.J. Thomson calculated the charge-to-mass ratio (e/m) using electric and magnetic fields
- The calculated ratio is -1.76 x 10^8 coulombs per gram (C/g)
Millikan Oil Drop Experiment
- Used to determine the charge (e) of an electron
- Measured the charge on oil droplets falling through an electric field
- Found that the charge on the droplets was always a multiple of a basic charge
Charge of Electron
- Millikan discovered that all charges were multiples of a basic charge, 1.6 x 10^-19 Coulombs
- The charge of an electron is -1.6 x 10^-19 Coulombs
Mass of Electron
- Using the e/m ratio (-1.76 x 10^8 C/g) and the calculated charge of the electron, the mass of the electron was determined
- The mass of the electron is 9.11 x 10^-28 g
Anode Ray (Positive Ray) (Canal Ray)
- The atom is electrically neutral, meaning there are positively charged particles to balance the negative charge of the electrons
- Eugen Goldstein experimentally proved the existence of protons
- The positive ray consists of positive ions of the gas used in the tube
Canal (anode) Rays
- Eugen Goldstein experimentally confirmed the existence of the canal rays
Explanation of production of positive rays
- High voltage ionizes the gas in the tube
- Positive ions of the gas constitute the canal ray
- They are the nuclei of the gas atoms and possess properties different from the cathode rays
Properties of anode rays
- Travel in straight lines
- Positively charged
- The Charge/Mass (q/m) ratio varies depending on the gas used
- The velocity of anode rays is much smaller than the velocity of cathode rays
Thomson’s Atomic Model
- The atom is a solid sphere of uniform positive electric charge (pudding)
- Negatively charged electrons (plums) are embedded in the sphere
- This model is sometimes referred to as the plum pudding model
Rutherford’s Scattering Experiment (Gold Foil Experiment)
- Rutherford fired alpha particles at a thin gold foil
- He observed that most of the alpha particles passed through the foil
- Some particles were deflected at small angles
- A very small number of particles were deflected at large angles
Rutherford Conclusions
- Most of the atom is empty space
- The nucleus is small, dense, and positively charged
- Electrons revolve around the nucleus
Rutherford Conclusions
- The atom contains a dense positively charged center called the nucleus
- The nucleus occupies only a small fraction of the atom's volume
- Electrons move around the nucleus in closed circular paths
- The number of electrons is equal to the number of protons, maintaining electrical neutrality
Planetary Model of Atom
- The atomic model resembles the solar system, with a positively charged nucleus at the center (like the sun) and negatively charged electrons orbiting it (like the planets)
Drawbacks of Rutherford’s Model
- The model could not explain the stability of the atom -- An orbiting electron should continually lose energy and spiral into the nucleus.
- The model could not explain the radiation emitted from some atoms
- Did not explain how the positive charges within the nucleus were held together.
Extra Mass
- The mass of a nucleus is greater than the sum of the masses of its protons and neutrons
- This extra mass is due to the binding energy of the nucleons
Discovery of Neutrons (Chadwick Experiment)
- James Chadwick proved the existence of neutrons (neutral particles)
- Chadwick bombarded Beryllium with alpha particles.
- The resulting radiation was neutral and was able to knock protons out of other atoms, revealing the presence of the neutron.
Chadwick's observations and conclusions
- When Beryllium was bombarded with alpha particles, neutral radiation was produced
- The radiation was able to knock protons out of other atoms, indicating the presence of material particles with no charge.
Chadwick’s observations and conclusions
- The radiation was able to move a paddle wheel, further suggesting the وجود جسيمات مادية (a material particle).
- The radiation did not deflect in an electric field, confirming the neutrality of the particles.
Atomic Number and Mass Number
- The atomic number (Z) is the number of protons in the nucleus of an atom.
- The mass number (A) is the total number of protons and neutrons in the nucleus of an atom.
Isotopes
- Isotopes are atoms of the same element with the same atomic number (same number of protons) but different mass numbers (different numbers of neutrons)
Hydrogen Isotopes
- Protium (¹H): One proton
- Deuterium (²H): One proton, one neutron
- Tritium (³H): One proton, two neutrons
Carbon Isotopes
- Carbon-12 (¹²C): Six protons, six neutrons
- Carbon-13 (¹³C): Six protons, seven neutrons
- Carbon-14 (¹⁴C): Six protons, eight neutrons
Oxygen Isotopes
- Oxygen-16 (¹⁶O): Eight protons, eight neutrons
- Oxygen-17 (¹⁷O): Eight protons, nine neutrons
- Oxygen-18 (¹⁸O): Eight protons, ten neutrons
Atomic Mass (Weight)
- The relative mass of an atom of an element, expressed in atomic mass units.
Atomic Mass (Weight) Scale
- Determined by the abundance of each isotope of an element in nature
- The average atomic mass is typically measured in atomic mass units (amu)
Atomic Mass Unit (amu)
- One atomic mass unit (amu) is equal to 1/12 the mass of a carbon-12 atom (¹²C)
Atomic Mass (Weight) of Chlorine (Cl)
- Two isotopes: ³⁵Cl and ³⁷Cl
- Average atomic mass of chlorine is calculated to be 35.45 amu based on the abundance of each isotope
Atomic Mass of Carbon (C)
- Average atomic mass of carbon is 12.011 amu, calculated considering the abundance of ¹²C, ¹³C, and ¹⁴C
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers key concepts from the cathode ray experiment including the properties of cathode rays, the charge-to-mass ratio calculated by J.J. Thomson, and Millikan's oil drop experiment. Test your knowledge on the characteristics and measurements related to electrons, including their charge and mass.
