Podcast
Questions and Answers
Rutherford's alpha-particle scattering experiment led to what conclusion about the structure of an atom?
Rutherford's alpha-particle scattering experiment led to what conclusion about the structure of an atom?
- Neutrons are present in the nucleus.
- Mass and energy are related.
- The mass and positive charge are concentrated in the nucleus. (correct)
- Atoms are electrically neutral.
Which statement is NOT true regarding cathode rays?
Which statement is NOT true regarding cathode rays?
- They possess kinetic energy.
- They produce mechanical pressure.
- They are electromagnetic waves. (correct)
- They produce heat.
The radius of a hydrogen atom in the ground state is 0.53 Å. What is the radius of $Li^{2+}$ in a similar state?
The radius of a hydrogen atom in the ground state is 0.53 Å. What is the radius of $Li^{2+}$ in a similar state?
- 0.265 Å
- 0.17 Å (correct)
- 1.06 Å
- 0.53 Å
The Bohr radius for a hydrogen atom (n=1) is approximately 0.530 Å. What is the radius for the first excited state (n=2)?
The Bohr radius for a hydrogen atom (n=1) is approximately 0.530 Å. What is the radius for the first excited state (n=2)?
In a hydrogen atom, the energy of the first excited state is -3.4 eV. What is the kinetic energy of the same orbit?
In a hydrogen atom, the energy of the first excited state is -3.4 eV. What is the kinetic energy of the same orbit?
The energy of the second Bohr orbit of the hydrogen atom is -328 kJ mol⁻¹. Determine the energy of the fourth Bohr orbit.
The energy of the second Bohr orbit of the hydrogen atom is -328 kJ mol⁻¹. Determine the energy of the fourth Bohr orbit.
In which of the following electronic transitions will minimum energy be absorbed?
In which of the following electronic transitions will minimum energy be absorbed?
According to Rutherford's model, what region of the atom contains nearly all of its mass?
According to Rutherford's model, what region of the atom contains nearly all of its mass?
One of the drawbacks of Rutherford's model is that it could not explain:
One of the drawbacks of Rutherford's model is that it could not explain:
What key assumption is made when applying the Bohr model to atoms or ions?
What key assumption is made when applying the Bohr model to atoms or ions?
According to Bohr's theory, what causes an electron to emit energy in the form of electromagnetic radiation?
According to Bohr's theory, what causes an electron to emit energy in the form of electromagnetic radiation?
Which of the following statements correctly describes a 'stationary orbit' in Bohr's atomic model?
Which of the following statements correctly describes a 'stationary orbit' in Bohr's atomic model?
If an electron moves from n=1 to n=3 in a hydrogen atom, how does the potential energy (PE) change?
If an electron moves from n=1 to n=3 in a hydrogen atom, how does the potential energy (PE) change?
What mathematical relationship did Bohr use to quantize the angular momentum of an electron in an atom?
What mathematical relationship did Bohr use to quantize the angular momentum of an electron in an atom?
Which of the following is a major limitation of the Bohr model of the atom?
Which of the following is a major limitation of the Bohr model of the atom?
What is the significance of the term 'Z' when applying the Bohr model to calculate the energy of an electron in a hydrogen-like species?
What is the significance of the term 'Z' when applying the Bohr model to calculate the energy of an electron in a hydrogen-like species?
How does the velocity of an electron in the Bohr model change as it orbits closer to the nucleus?
How does the velocity of an electron in the Bohr model change as it orbits closer to the nucleus?
Which scientist is credited with discovering the atomic nucleus through the gold foil experiment?
Which scientist is credited with discovering the atomic nucleus through the gold foil experiment?
What type of particles were used in Rutherford's scattering experiment?
What type of particles were used in Rutherford's scattering experiment?
What aspect of atomic structure did J.J. Thomson's model primarily address?
What aspect of atomic structure did J.J. Thomson's model primarily address?
Why is the Bohr model not applicable to multi-electron species?
Why is the Bohr model not applicable to multi-electron species?
What concept did Bohr introduce to explain the stability of the atom, which was lacking in Rutherford's model?
What concept did Bohr introduce to explain the stability of the atom, which was lacking in Rutherford's model?
According to Bohr's postulates, when does an atom emit radiation?
According to Bohr's postulates, when does an atom emit radiation?
If 'n' represents the principal quantum number, how does the energy of an electron in a hydrogen atom change as 'n' increases?
If 'n' represents the principal quantum number, how does the energy of an electron in a hydrogen atom change as 'n' increases?
Which of the following best describes the shape of electron orbits in Bohr's atomic model?
Which of the following best describes the shape of electron orbits in Bohr's atomic model?
In the context of the Bohr model, what happens to the radius of an electron's orbit as the principal quantum number 'n' increases?
In the context of the Bohr model, what happens to the radius of an electron's orbit as the principal quantum number 'n' increases?
What experimental observation led Rutherford to conclude that the atom is mostly empty space?
What experimental observation led Rutherford to conclude that the atom is mostly empty space?
Which of the provided options provides the best explanation of why Rutherford's model was ultimately considered incomplete?
Which of the provided options provides the best explanation of why Rutherford's model was ultimately considered incomplete?
Flashcards
Rutherford Model
Rutherford Model
An atomic model where nearly all of the mass and positive charge is concentrated in a small region called the nucleus.
Rutherford Model Drawbacks
Rutherford Model Drawbacks
Rutherford's model could not explain the stability of atoms or information about electron distribution.
Bohr's Model: Stationary Orbits
Bohr's Model: Stationary Orbits
Electrons revolve in stationary orbits without losing energy.
Bohr Model of Atom
Bohr Model of Atom
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Major Drawback of Bohr Model
Major Drawback of Bohr Model
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Bohr Formula Validity
Bohr Formula Validity
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Rutherford's Conclusion
Rutherford's Conclusion
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Cathode Rays
Cathode Rays
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Ground state
Ground state
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1st excited state
1st excited state
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Calculate KE
Calculate KE
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Second Bohr Orbit`s enery
Second Bohr Orbit`s enery
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Study Notes
- The lecture focuses on atomic structure, specifically Bohr's model
Rutherford's Model
- In Rutherford's model, the atom’s entire mass and positive charge are concentrated in a small region called the nucleus.
- The approximate size of the nucleus is 10^-15 meters
- Electrons revolve around the nucleus in circular orbits according to the Rutherford Model
Drawbacks of Rutherford's Model
- Rutherford's model could not explain the stability of atoms.
- According to classical electromagnetic theory, electrons should lose energy and spiral into the nucleus
- The model provided no information about the distribution of electrons
Bohr's Model
- Bohr's model addresses the limitations of Rutherford's model by explaining the stability of the atom
- It introduces the concept of stationary orbits: electrons revolve in specific orbits without losing energy
- Electrons can only occupy certain orbits with fixed energy levels
- When an electron is revolving in a stationary orbit it will not lose its energy
- mvr = nh/2π, where m is mass, v is velocity, r is the radius, n is the orbit number, and h is Planck's constant
- mv²/r = 1/(4πε₀) * (Ze)e / r² which can be expressed as mv²/r = KZe²/r²
Calculations based on Bohr's Model
- vn = 2.186 x 10^6 m/s * (Z/n), where vn is velocity, Z is atomic number, and n is the principal quantum number
- rn = 0.529 Å * (n²/Z), where rn is radius, n is the principal quantum number, and Z is the atomic number
- Potential Energy (PE) = -2 * 13.6 * (Z²/n²) eV
- Kinetic Energy (KE) = +13.6 * (Z²/n²) eV
- Total Energy (PE + KE) = -13.6 * (Z²/n²) eV
- 1 eV = 1.6 x 10^-19 J
- Shell numbers: K shell corresponds to n=1, L shell to n=2, M shell to n=3, and N shell to n=4
Major Drawbacks of Bohr's Model
- The model does not account for electron-electron repulsion in multi-electron atoms
- Bohr's formula is only valid for single-electron atoms or ions.
- Single electron atom or ions include H, He+, Li+2, Be+3 and Na+10
Additional Information and Formulae
- Ground state corresponds to n=1
- First excited state corresponds to n=2
- Second excited state corresponds to n=3
Example Questions
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Rutherford's alpha-particle scattering experiments led to the conclusion that the mass and positive charge of an atom are concentrated in the nucleus
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Which of the following is never true for cathode rays: They are electromagnetic waves, cathode rays are a beam of electrons
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The radius of the hydrogen atom in the ground state is 0.53 Å. The radius of Li2+ in a similar state is 0.17 Å
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Bohr radius for the hydrogen atom (n=1) is approximately 0.53 Å. The radius for the first excited state (n = 2) is 2.12 Å
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In a hydrogen atom, if the energy of the first excited state is -3.4 eV, then the kinetic energy (KE) of the same orbit of the hydrogen atom is +3.4 eV
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The energy of the second Bohr orbit of the hydrogen atom is -328 kJ mol^-1, therefore, the energy of the fourth Bohr orbit would be -82 kJ mol^-1
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Minimum energy absorbed in electronic transitions often involves transitions between higher energy levels with smaller gaps
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In which of the following transitions is minimum energy absorbed: n=4 to n=5
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Energy level diagram illustration:
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n=6 has an energy level of -1.51
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n=3 has an energy level of -3.4 ev
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n=1 has an energy level of -13.6
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